In this Outside the Lines report, Bob Costas talks for the first time about his removal from last year's Super Bowl telecast. (2:19)

IN DECEMBER 2015, the movie "Concussion" was set for a Christmas Day release in nearly 3,000 theaters across America. The film told the story of the NFL's attempts to discredit research tying brain damage to football, and Bob Costas wanted to address it on national television.

Over the previous decade, Costas had become the face of football on NBC, hosting one of TV's most-watched programs, "Sunday Night Football." As part of every broadcast, Costas would take two minutes at halftime to speak directly to the program's 18 million viewers about the NFL issues of the day. Mostly, his commentaries were celebrations of the sport -- Brady vs. Manning, a tribute to Lambeau Field -- but, occasionally, he addressed subjects like gun control or the controversial name of the Washington, D.C., football team.

With his 28 Emmys and eight National Sportscaster of the Year awards, Costas had become the most-respected broadcaster of his generation -- a kind of Walter Cronkite for sports. He believed it was his responsibility to address uncomfortable truths, or "elephants in the room," as he often called them.

The release of "Concussion" seemed a natural topic given the nationwide awakening about head trauma in contact sports, especially the NFL. Costas believed it was important to have viewers confront football's existential crisis and consider their own moral dilemma as fans complicit to the sport's carnage.

Yet he recognized such a speech posed a challenge for his bosses and NBC. The network was paying the NFL billions to air games on Sunday nights. Even more, Costas knew NBC executives were hoping to expand the network's NFL package to Thursdays.

Costas sent the essay to his bosses for approval, something he typically did not do -- and waited.

What would ensue that week -- and in the years that followed -- reveals for the first time how a broadcasting icon went from fronting America's most popular sport to being excised from last year's Super Bowl and, ultimately, ending his nearly 40-year career with NBC.

Outside the Lines spoke with the 66-year-old Costas dozens of times over the course of the past year. Those conversations provide not only the never-before-told backstory of how he became an NFL outsider, but also deep insight into his personality: the intelligence and self-assurance that have driven his career; the years-long struggle as he reconciled the celebration of a sport that enriched him financially and helped make him a broadcasting icon, but also weighed so heavily on his conscience; and the insecurity and intense worry -- near agony -- about the possibility of betraying his colleagues and friends by sharing his story. All of it points to the all-encompassing influence of the NFL -- even over the most distinguished broadcaster of his era.

In the end, Costas wished he had never spoken to Outside the Lines about any of it: "The upside is not equal to the fear I have."

At his career peak, Bob Costas was everywhere -- Super Bowl, World Series, NBA Finals, Olympics, Kentucky Derby, golf, boxing, hockey, and on and on. NBC even created a talk show for him, "Later," which lasted for seven seasons. NBC/NBCU Photo Bank via Getty Images

BY DECEMBER 2015, nobody at NBC should have been surprised that Bob Costas would want to speak his mind about football. After joining the network at age 27 in 1979, he had become one of NBC's signature go-to voices.

With NBC Sports chairman Dick Ebersol as his champion, Costas established himself as somebody who could do just about anything: play-by-play, commentary, hosting, interviewing.

He was everywhere -- Super Bowl, World Series, NBA Finals, Olympics, Kentucky Derby, golf, boxing, hockey, and on and on. NBC even created a talk show for him, "Later," which lasted for seven seasons and displayed his interviewing talents. The diversity of people Costas interviewed over the years is mind-boggling, speaking to his intelligence and utility: From Johnny Cash to Dr. Ruth Westheimer, Tom Jones to Pierre Salinger, Gary Busey to Ozzy Osbourne, William Shatner to Charlton Heston.

It's not just that he was comfortable outside of sports, it's that he melded a near-photographic memory with a genuine interest and passion for pop culture, politics and history.

"Look, the guy was not only talented, but he had just a great amount of credibility built up between hosting, play-by-play, studio work, his show -- remember, he hosted his own show!" says Vince Wladika, who spent 11 years as a communications executive at Fox and NBC, working with Costas from 1989 to 1994. "Between all that exposure, the audience trusted him. ... There was never an issue with Bob's willingness to speak his mind."

Wladika recalled an incident during the 1993 NBA Finals when Costas interviewed then-commissioner David Stern in the throes of gambling allegations involving Michael Jordan. The interview grew contentious, and as Costas pressed Stern about Jordan's alleged gambling debts, the commissioner snapped: "How much money do you owe?" To which Costas retorted, "It doesn't matter. I don't represent the NBA."

When the interview ended, Costas says Ebersol expressed his displeasure.

"Dick would have preferred to give the league a little easier ride," Costas says. "In the end, he always understood I had my view of things. In the big picture, we always worked it out, but there were times when I went off what they would have preferred was the script."

This, Costas says, was hardly unusual throughout his career at NBC -- though he and Ebersol remain close and Costas had nothing but glowing things to say about his mentor. Ebersol declined to be interviewed for this story.

Costas told Outside the Lines that his credibility -- and, frankly, that of the network -- relied on his willingness to address hard topics.

Few subjects are sacred to Costas, even his beloved baseball. Anyone who knows anything about Costas knows that he genuflects to the sport in ways that make non-baseball fans cringe. Still, Costas says he felt obligated to address the steroid scandal as it consumed the sport throughout the 2000s. "A friend of mine said ... 'Whether it's news or sports, you can never go wrong being on the right side of history,'" Costas says. "I was right about steroids in baseball, and I was the only network broadcaster who even mentioned it. And I mentioned it all the damn time."

Costas says he never heard from Major League Baseball executives or any of his bosses when he talked openly on MLB broadcasts about how the game's most hallowed records were being devalued as baseball's hierarchy stood by.

There were times, though, when Costas was seen as less aggressive. He hosted his first Olympics in 1992, in the midst of Juan Antonio Samaranch's 21-year run as IOC president. In 1996, journalist Frank Deford conducted a devastating interview of Samaranch for HBO's "Real Sports," in which he confronted the Olympics chief about his ties to the fascist Spanish dictator Francisco Franco and the fact that he had honored Romanian tyrant Nicolae Ceausescu. In a New York Times piece about the interview, TV critic Richard Sandomir wrote: "Nothing quite so controversial occurs Wednesday at 9 p.m. during 'Prelude to the Games,' the two-hour Olympic preview show produced by Sports Illustrated TV for NBC. Nothing harshly critical of the I.O.C., other Olympic organizations or sponsors is said on the special with Bob Costas as host."

Of Samaranch's ties to the dictators and why he didn't confront the topic, Costas told Outside the Lines: "If I had interviewed Samaranch, I would have, but Samaranch did not appear for an interview with me."

Costas did, however, use the moment of the Ukrainian women's biathlon team taking gold in the 2014 Sochi Games as an opportunity to address Russia's intervention in the country, its "hostile" record on gay rights and its sponsorship of a vicious regime in Syria.

After joining the network at age 27 in 1979, Costas quickly became one of the network's signature go-to voices. Focus on Sport/Getty Images

IN THE SPRING of 2005, NBC, led by Ebersol, agreed to pay the NFL $600 million per year to televise its games on Sunday nights. The decision was a direct response to declining viewership, especially among the network's most sought-after demographic: men, age 18-49.

NBC had fled the football arms race back in 1997, complaining that rights fees had risen out of control. Fox had drastically altered the landscape in 1993 when it agreed to pay nearly $400 million per year to air NFL games -- a move that left CBS, the league's original TV partner, out of the NFL package and had practically destroyed the network.

"Without the NFL, who could possibly exist? CBS almost proved nobody could," says former TV executive Rick Gentile, who was with CBS from 1982 to 1998 and oversaw coverage of some of the world's biggest sporting events, including several Super Bowls. "As soon as we lost the NFL, we lost like 16 of our best [affiliate] stations to Fox. It was a devastating blow for the network, and it literally took years and years to pull out." In 1994, CBS balked at paying $295 million, he says, but when the network got another chance, it was "'How much do you need? Here's the check, fill in the number.'"

So in 2005, cognizant of CBS's free fall, NBC committed $3.6 billion over the coming six seasons to get back into the NFL fold. "NBC Decides It Can't Live Without Football," declared a headline in The New York Times.

At the time, Costas says he had sworn off the sport. He had hosted NBC's NFL pregame show for nearly a decade in the '80s and early '90s but asked to be taken off the broadcasts after the 1993 season.

"As I got closer and closer to the game, I became ambivalent about it," he says. "The sheer violence of the game, and then the celebration of that violence, even before CTE became a specific issue ... I just didn't feel comfortable with that. That felt stupid to me."

Costas did host "Inside the NFL" on HBO for six seasons beginning in 2002, but he says he justified that in his mind because the show provided autonomy to offer commentary and typically conveyed a level of journalism.

But when NBC returned to football in 2005, Costas says Ebersol asked him to return as host and he agreed "out of loyalty" and "as kind of a good soldier."

Over the next decade, NBC would own Sunday nights, and Costas would become the emcee of "Football Night in America," setting the tone for a five-hour broadcast every week. He had a reputation as a trustworthy and reasoned voice, someone who was willing to offer his opinion but not shout it out like a carnival barker.

At the same time, his relationship with football was growing increasingly complicated. As evidence mounted tying the sport to brain disease, Costas says he felt compelled to talk about it. During Week 2 of the 2010 season, following a series of high-profile, concussion-related incidents, Costas presented his first essay about the topic to NBC viewers.

"More and more is being learned about the now-undeniable link between concussions especially repeat concussions -- and subsequent problems with dementia, depression, early onset Alzheimer's, an entire array of serious medical problems stemming from an injury that is more common in football than in most other sports."

"Here's the truth," Costas said. "America's most popular sport is a fundamentally dangerous game where the risk of catastrophic injury is not incidental, it is significant."

It was a decisive moment in the history of football in America. Here was the preeminent voice of televised sports, looking straight into the camera, telling millions of fans who tuned in that he, they -- all of us -- were essentially complicit in the human destruction caused by a gladiator sport. Equally surreal -- but unstated -- was the fact that even as Costas was describing the problem as "undeniable," the NFL was publicly denying any link between football and brain damage.

In the ensuing years, as research accumulated, Costas became more emboldened. His blend of humor, wit and unfiltered opinion was gold on the talk-show circuit -- from CNN to Bill Maher to NBC's "Today" show -- as well as to anyone who wanted to discuss the dangers of football.

In 2011, in a conversation with Robert Lipsyte of The New York Times, he told an audience, "The game is unacceptably brutal. Can I say it any more clearly than that it is unacceptably brutal?" Two years later, on NBC's "Meet the Press," he said, "The way football is currently played in the NFL is fundamentally unsustainable." And the following year, on "The Last Word," he called the sport "inherently violent and brutal" and suggested that head trauma could lead to off-field criminal conduct by some players.

Costas says he never heard from anyone with the NFL complaining about his statements, nor does he say his bosses at NBC protested or suggested they had ever been contacted by league officials.

Gentile, the former CBS executive, says it wouldn't surprise him that Costas never received complaints from the NFL -- because the league officials always called Gentile and not the broadcaster himself when they had concerns. Still, Gentile says, the NFL was "never really dictatorial, at least in my lifetime." It was nothing like, for example, the network's relationship with The Masters, which kept intense pressure on CBS by signing only one-year contracts.

And so it was that The Masters could force the network to banish Gary McCord from the broadcast for describing Augusta National's speedy greens as "bikini-waxed," or Jack Whitaker for referring to a "mob" of fans on the 18th green at the end of a playoff.

Gentile, though, understands why the NFL might have become more controlling over time.

"It's an existential issue," says Gentile, who also is the director of the Seton Hall University Sports Poll, which conducts regular surveys on sports-related issues. "The NFL is faced with this looming head-injury issue. We conducted polls at Seton Hall and you could see the numbers go up of parents who didn't want their kids to play football. That doesn't speak well to the future, so I think there's a strong sensitivity there [from the NFL]. This is, 'Do we exist or not.'

"And it's just as important to the networks that the NFL continue to be the NFL."

So the more Costas talked definitively about the connection between football and brain damage, the more it created tension between him, his bosses and the NFL.

Something was bound to give.

Costas attended a 2015 screening of "Concussion" and was moved by the film's portrayal of Dr. Bennet Omalu, the neuropathologist who first posited that former NFL players had died with a brain disease caused by football. Andrew Toth/FilmMagic

TO UNDERSTAND THE symbiotic relationships between the television networks and the NFL requires acknowledging the obvious: An undeniable power imbalance exists. The NFL -- like other leagues -- has several options to air games and highlights, from the Big Three networks to ESPN and a variety of cable venues -- and now Facebook, Google, Amazon and other developing media. But there's only one NFL, and only so many games to go around. The result is a financial windfall for the league.

The NFL took in more than $7 billion from its television partners this season. By 2027, according to a USA Today report citing the sports analytics firm Navigate Research, that number could hit $17 billion -- meaning each of the league's 32 teams would pocket more than a half-billion dollars from TV every year.

At ESPN, the network is in the middle of a contract that pays the NFL $1.9 billion per year to air Monday Night Football, a deal set to expire in 2021.

These are partnerships, but they tilt heavily toward the league's Park Avenue offices.

Says Costas: "Look, the NFL isn't just the most important sports property, it's the single-most important property in all of American television. And it isn't even close."

Because of the stakes, the NFL has enormous influence over how networks portray the sport. When a broadcaster like Costas goes rogue, or investigative reporting touches on sensitive issues like concussions or politics, tensions inevitably surface.

Those tensions have surfaced at ESPN, which famously cancelled its popular 2003 series Playmakers after only one season following complaints from the NFL. Outside the Lines' yearslong reporting on football's concussion crisis has led to numerous complaints from the NFL.

In 2013, ESPN abruptly ended a partnership with PBS's award-winning program "Frontline" on "League of Denial," a documentary that explored the NFL's two-decade effort to deny and rewrite the science connecting football and brain disease. After ESPN pulled out of the deal, The New York Times published a story that suggested the network had bowed to pressure from the NFL. ESPN denied it, saying it dropped out over lack of "editorial control." ESPN ended up running excerpts from the film and a companion book, as planned, and it continues to cover the concussion issue to this day.

Says Costas: "The networks, all of them, dance to the NFL's tune. It's just kind of the way it goes. Everyone walks on eggshells around the NFL."

Costas and his mentor and friend, former NBC Sports chairman Dick Ebersol. Robin Platzer/FilmMagic

IN 2015, COSTAS was invited to a November screening of "Concussion" in Hollywood. He was moved by the film and even thought Will Smith might earn an Oscar nod for his performance as Dr. Bennet Omalu, the neuropathologist who had ignited the NFL's concussion crisis a decade earlier by first positing that former players had died with a brain disease caused by football.

NBC was scheduled to air Indianapolis at Pittsburgh on Dec. 6. The movie was set largely in Pittsburgh, and former Steelers great Mike Webster was a major character in the story.

"It was a natural lead-in," Costas told Outside the Lines. "I thought that the movie would make an impact, and I thought this was a way not only for NBC to acknowledge it, but to get out in front of it."

Costas typically wrote his essays on the fly on game day, sometimes even as the first quarter of the Sunday night matchup was under way. This time, though, he wrote it in advance to give his bosses an early look, recognizing it could create problems.

The essay, which has never been made public but was provided to Outside the Lines, began with a description of Omalu as "the neuropathologist who clearly demonstrated what just about everybody now understands -- but which for years the league denied: There is a direct and often tragic link between football and brain damage."

Costas says he sought to mitigate the potential embarrassment for the NFL by highlighting its efforts to improve player safety. "I purposely toned it down," he says.

He wrote, "To its credit, the NFL now has put millions into medical research and the possibility of improving equipment. They have instituted rules changes aimed at making the game safer, awareness programs aimed at youth football, and stricter head trauma protocols, which, even if they don't always work, at least appear to be a step in the right direction."

But Costas didn't hold back: "Even as the ratings rise, so, too, does a certain ambivalence. Because as much as we may try to push it into the background, there's a kind of Russian roulette going on on the field tonight and on our television screens throughout the fall and winter, since we know that for all the game's appeal, many of its participants will one day pay dearly for their part in our national obsession."

Costas says he submitted the essay to Ebersol's successor, NBC Sports chairman Mark Lazarus, and executive producer Sam Flood and awaited their response.

"I remember the reaction almost verbatim. They said, 'This is a very well-written piece, wouldn't change a comma. We can't air it."

Costas says he asked why.

"We're in negotiations with the NFL for Thursday Night Football," he says he was told.

"It was at that point that I realized that this was an untenable situation for me," he says. "I knew my days there were numbered."

Lazarus and Flood did not respond to requests seeking comment for this story. An NBC spokesman provided a statement that read, "We have historically given our commentators a lot of leeway to speak on our air about issues and controversies, and Bob has benefited most from this policy. We're very disappointed that after 40 years with NBC, he has chosen to mischaracterize and share these private interactions."

Even before he offered the "Concussion" essay, the tension had ratcheted up between Costas and the network. At the start of the season, the NFL had introduced an ad campaign called "Football is Family." The spots were designed, in part, to counter negative publicity that had come to surround the league, especially around head trauma. One ad showed female fans wearing their favorite team gear, working out, drinking coffee, taking walks with their similarly decked-out children; another had Packers running back Eddie Lacy mowing the lawns of fans who lived near Lambeau Field.

By the time the divisional playoffs rolled around -- less than two months after his "Concussion" essay was killed -- Costas had had enough. In speaking with Bob Raissman of the New York Daily News, he said of the league's promotion: "It's a little much to take, while watching a game, that you are constantly bombarded with 'Football is Family' [commercials]."

He described to Raissman the significant number of players "acting like creeps and criminals" and concluded with, "You see all this stuff and the first thing that comes to mind is not a Norman Rockwell painting. Yes, 'Football is Family.' Bring out the hearts and the tinkling piano music, because it really is a touching tableau."

It didn't take long for Costas to hear from his bosses: Why did he need to take such a gratuitous potshot at NBC's biggest business partner?

"My response was, 'The purpose of it is so I can sleep at night,' you know?" he told Outside the Lines. "Some of this is like blinking in a hostage video. It's like, 'You know I sort of have to do this. I hope you get what I'm really thinking right now.'"

Two months after Costas' "Concussion" essay was rejected and two weeks after he ridiculed the "Football is Family" ads, the NFL announced a contract with NBC to air five Thursday night games in each of the following two seasons. NBC would pay the league another $450 million -- or $45 million per game -- to share the broadcast rights and simulcast the games on the league's own NFL Network.

When NBC returned to football in 2005, Costas agreed to return as host "out of loyalty" and "as kind of a good soldier" to NBC. Over the next decade, NBC would own Sunday nights, and Costas would become the emcee of "Football Night in America." AP Photo/Matt Rourke

BY THE TIME NBC was officially signing its new deal, Costas says he had invoked a clause in his contract that would allow him to step away from football and the Olympics to take on an emeritus role. He would host one more season on Sunday nights and then turn the show over to Mike Tirico. Costas' NFL swan song would be Feb. 4, 2018, when NBC next aired the Super Bowl.

But three months before the Super Bowl, the plan imploded during one dramatic week. First, on Nov. 7, 2017, Costas appeared at a journalism symposium at the University of Maryland.

There, he told a crowd of more than 400, "The issue [in sports] that is most substantial -- the existential issue -- is the nature of football itself."

He then went on a nearly one-and-a-half minute riff about football and brain damage that was punctuated by this statement: "The reality is that this game destroys people's brains -- not everyone's, but a substantial number. It's not a small number, it's a considerable number. It destroys their brains."

Two nights later, Costas was honored by the Concussion Legacy Foundation -- an advocacy group affiliated with researchers who have been at the forefront of the science connecting football and brain disease. Costas accepted the award from CLF to a standing ovation.

By this point, Costas' line at Maryland -- This game destroys people's brains -- had gone viral, raising hackles in the NBC offices. The New York Daily News asked NBC for comment, and a spokesman responded, "Bob's opinions are his own, and they do not represent those of the NBC Sports Group" -- prompting a story from Raissman under the headline, "NBC throws Bob Costas under the bus and in the process sends warning to rest of its talent."

Sensing a budding problem with his employer, Costas says he decided to appear on CNN on Saturday morning to make it clear he wasn't being critical of NBC. So, for the third time in a week, Costas was talking publicly about football and brain damage. He didn't soften any of his comments -- in fact, he reiterated them -- but he did attempt to defend the network.

"I've been saying these things for the better part of a decade, and often on NBC, in front of the biggest audience not just in all of sports, but in all of television -- 'Sunday Night Football,'" Costas told host Michael Smerconish. "And I think NBC Sports deserves credit for this."

Within an hour, Costas says he received a text from Flood, who oversees sports production for NBC.

"I think the words were, 'You've crossed the line,'" says Costas, who says he no longer has the text.

"My thought was, 'What line have I crossed?'"

Later, Costas says he pointed out that he had been saying these things about football for years -- often on NBC. That didn't matter; it seemed this was one time too many.

Costas was told he was off the Super Bowl LII broadcast.

"I recall the phrase, 'It's a six-hour, daylong celebration of football, and you're not the right person to celebrate football,'" Costas says. "To which my response was not, 'Oh please, please, change your mind.' My response was, 'Yeah, I guess you're right.'"

Costas insists that rather than being upset or feeling punished, he felt relief. Still, he says he and NBC recognized that pulling him off the Super Bowl would raise questions. Costas had a proposal: He should interview Roger Goodell.

"I was looking out not only for myself, because I'd like to do the interview, but I was also looking out for NBC because that would have taken them off the public relations hook and eliminated all the confusion about them supposedly kicking me to the curb or throwing me under the bus."

Costas says Lazarus and Flood told him they would check with the NFL. The answer came back quickly: Goodell wouldn't do it.

"I don't know how far they went," Costas says, positing that they could have demurred without argument "as opposed to what you could say, which is this: 'Hey, we pay you guys billions of dollars, and 99 percent of what we do celebrates and promotes the league. Don't you have some obligation to us here? It's our year in the three-year Super Bowl cycle.' I don't know if that kind of pushback took place.'"

Costas says he had asked to interview Goodell before Super Bowl XLIX but been rebuffed then, too. This was not the norm across all sports. Costas says he had regularly interviewed league commissioners during their championships.

"It tells you who calls the shots," Costas says. "The only business arrangement I can think of where the buyer must continually flatter the seller is the sports TV business. 'We're pulling a Brinks armored truck up to Park Avenue, Mr. Goodell. It contains the billions of dollars that we're going to pay you for the right and privilege to televise your games. But if we've delivered them in a denomination that does not please you, we're terribly sorry, we'll back the truck up, and we'll bring it to you in 20s and 50s if that's the way you'd prefer it.'"

NFL spokesman Brian McCarthy told Outside the Lines in an email that, often, each network airing the Super Bowl asks for an interview with the commissioner. "Commissioner Goodell has done one sit-down interview in the last five years with the network airing the Super Bowl," says McCarthy. "That was for the 50th Super Bowl in 2016. Commissioner Goodell has not done an interview with NBC for the four Super Bowls it has aired since he has been commissioner."

McCarthy says the NFL did not ask NBC to remove Costas from the Super Bowl.

In the days before the Super Bowl, when NBC first revealed that Costas wouldn't be part of the coverage, statements released by the network suggested that he wasn't doing the game in deference to Liam McHugh and Dan Patrick, who had served as "Sunday Night Football" hosts throughout the season. Costas was quoted: "It wouldn't be right for me to parachute in and do the Super Bowl" -- even though that had been precisely the plan before things went awry.

The next day, in an email to Sports Business Daily, Costas wrote, "The decision was mutually agreeable, and not only do I not have a problem with it, I am actually happy about it. I have long had ambivalent feelings about football, so at this point, it's better to leave the hosting to those who are more enthusiastic about it."

That was only partially true.

Says Costas now: "I was hoping that the whole thing wouldn't cause a stir. And what I said was true as far as it went. I was completely comfortable with it, I had no personal stake in hosting, I was happy football was in my rearview mirror."

In his statements to Sports Business Daily, he had also dismissed any suggestion that his comments at Maryland had prompted NBC to pull him from the game. He wrote about how he had been making these same kinds of comments about football for a long time, "So the idea that I am only now finding my voice on this, or that NBC was taken aback by what I said at Maryland is just wrong. It's all simple and straightforward."

Except that it wasn't.

Costas is the only person to win sports, news and entertainment Emmy Awards. Marc Bryan-Brown/WireImage

IN DECEMBER, COSTAS was inducted into the Sports Broadcasting Hall of Fame. At the ceremony, he singled out Lazarus and Flood.

Of Lazarus, he said, "If there is a better, more reasonable person in a prominent position in network sports than Mark Lazarus, I haven't met him or her."

There was nothing surprising about this. For the better part of a year, during dozens of conversations with Outside the Lines -- short ones, long ones, in person, on the phone -- Costas made a point of noting how, in spite of everything he was saying, he had no issues with anyone at NBC.

"Toward the end, I was something of a square peg in a round hole," he said during his induction speech, a phrase he had used repeatedly with Outside the Lines.

What was surprising about Costas was not that he was concerned that he might offend anyone at NBC, but how concerned he was. Over the past few months, rarely did a conversation take place without Outside the Lines having to reassure Costas that the story would reflect his respect and admiration for his colleagues, and that he held no ill will toward them or NBC.

Yet, it didn't seem to matter. The conversations would end, Costas would appear to trust the process, and then, days or weeks later, it was like Groundhog Day and the same conversation would occur again. Costas also was concerned with what internet trolls and commenters might say about him after they read the story. Asked why he cared so much when it was clear he couldn't satisfy everyone, Costas replied, "I guess I find unfairness or untruth annoying." He had suggestions for how to phrase and contextualize certain elements of the piece, and he regularly lamented that some people might perceive him as bitter -- again, despite regular assurances that the story would not reflect him as bitter.

The reporting on Costas revealed not only his mixed feelings about revisiting the more difficult portion of his career, but also NBC's reaction to him making it public. NBC declined to license ESPN its footage involving Costas in a video version of this story that aired on E:60. Costas repeatedly suggested that Outside the Lines reach out to his longtime NBC producer and one of his closest friends, Bruce Cornblatt, saying he would be an excellent resource who would be happy to talk. Cornblatt, though, did not respond to calls and, ultimately, sent a text saying he declined to comment; asked why, Cornblatt didn't respond. Outside the Lines asked an NBC spokesman whether Cornblatt had been told not to cooperate, and the spokesman denied that was the case.

In the end, Costas says he regretted ever taking part in the story; not because he regretted his comments about football, but because of the strain it created around his relationships with NBC colleagues.

Taken as a whole, it reflected something Costas said in one fashion or another during several conversations with Outside the Lines: As much as he cherished his time at NBC, he and the network simply had reached a point of divergent interests.

"I am not a Howard Cosell at the end of his career deciding he doesn't like boxing," Costas says. "I decided long ago that I had misgivings about football, and I tried to use the forum they gave me to make those points. They gave me bits and pieces, but eventually they took those bits and pieces away from me."

When Costas had decided he wanted to stop hosting Super Bowls and Olympics, the plan was to take on an emeritus role that would have him appearing to host or offer commentary on select major events or programs. Instead, Costas and NBC agreed to terms this past fall to end his contract early. Costas had said at one point that he expected a joint announcement in January, with both sides releasing statements that described their mutual respect and admiration. Instead, the news trickled out when Costas confirmed it to the New York Post in a Jan. 19 story headlined, "Bob Costas and NBC are quietly and officially broken up."

"It's very fair and very amicable," Costas told Outside the Lines. "It was a very, very fruitful run of nearly four decades, and I have nothing but respect and appreciation for all of it."

David Lubbers, a producer in ESPN's enterprise and investigative unit, and Julia Theaman, a content associate for Outside the Lines and E:60, contributed to this report.