Lincoln Riley, the youngest FBS coach at 33 years old, talks about his relationship with recently retired Sooners coach Bob Stoops. (2:22)

NORMAN, Okla. -- When Matt McMillen arrived at Bob Stoops' house on June 5, he had no reason to suspect this dinner would be any different from the usual.

As Oklahoma's football operations director and Stoops' right-hand man for nearly two decades, McMillen had long been counted among Stoops' most trusted friends. Their two families even ate dinner together at least a couple of times a week.

But on this evening, as Stoops flipped the chicken on the grill, he was unusually quiet, McMillen noticed. Then, as they sat to eat, Stoops dropped the bombshell.

"Matty," he began, "I'm not going to coach anymore."

Recently retired Oklahoma coach Bob Stoops said he'd be open to a conversation about joining the College Football Playoff selection committee. AP Photo/Sue Ogrocki

For the next half-hour, McMillen was the one who couldn't speak.

"I couldn't think of anything to say," McMillen said. "Couldn't even ask a question. That's how blindsided I was."

Two days later, all of college football would feel the same.

After the turn of the millennium, no coach in the country enjoyed more consistent year-to-year success than Stoops. In 18 seasons, he won 10 Big 12 titles, more than the rest of the league combined. He also captured a national title in 2000, played for three more, and made the 2015 College Football Playoff.

Yet, while relatively young by coaching standards at 56, Stoops had been contemplating his exit strategy years before he stunningly retired June 7 and turned the program over to Lincoln Riley.

In 2010, Stoops told his mentor, Steve Spurrier, that there would be "no way" he would still be coaching at 65, the age Spurrier was at the time.

"I thought about it years ago, that's true," Stoops said. "Reflecting on, how long do you want to do this? Not that anything was imminent. But life changes for everybody year to year.

"Everything has its time."

Armed with another loaded team coming off back-to-back Big 12 titles, it didn't seem as if this would be that time. Even to those closest to him.

"He said forever he wasn't going to coach until he was old," McMillen said. "But as you get older, 50-whatever doesn't seem very old. When you get to that age, maybe you think 65 is old.

"That's why I didn't think it was going to be as soon as it was. I thought it was a two- or three-year window away."

But it wasn't.

What happened to Stoops' father almost 30 years ago is one reason why.

On Oct. 7, 1988, Ron Sr. was still coaching defense for Cardinal Mooney, Stoops' high school alma mater in Youngstown, Ohio. That night, Stoops' older brother, Ron Jr., was an assistant for the opponent, rival Boardman. As time expired in regulation, Mooney scored a game-tying touchdown, but missed the extra point that would've won the game. That's when Ron Sr. began to feel ill, forcing him to lie down on the benches. He watched as Mooney prevailed in triple-overtime, before being placed into an ambulance. On the way to the hospital, he died of a heart attack. He was 54.

Stoops has been diligent about his health, monitoring his cholesterol and his heart, and making exercising a priority. But his dad stayed in terrific shape, too, playing competitive baseball in Youngstown into his 50s.

Having passed the age at which his father died, Stoops didn't want coaching to take him away from his family, the way it did his dad.

"It's something you're just always aware of," said Stoops, who has kept his father's state title ring inside a wooden case with his Oklahoma championship jewelry. "That history is there. It's why we are who we are."

Perhaps the boldest move Stoops ever made at Oklahoma came three years ago, when he fired offensive coordinator Josh Heupel, who was the quarterback of Stoops' national championship team.

To replace him following a disappointing 8-5 season that ended in an embarrassing 40-6 bowl loss to Clemson, Stoops put his offense in the hands of Riley, who was a 31-year-old Mike Leach protégé.

In Riley, Stoops saw a young coach who resembled him. Others at Oklahoma saw the connection, down to their staccato-speaking mannerism.

In the way Stoops immediately turned the Sooners around after arriving, Riley instantly revived the Oklahoma offense. In the two years since, the Sooners have dropped only one Big 12 game, while owning the nation's No. 3 and No. 4 scoring offenses.

Bob Stoops handed off a ready-made playoff contender with a senior QB. Matthew Stockman/Getty Images

In May, Oklahoma rewarded Riley with a $1.3 million extension, the largest payout to an assistant in school history. The ultimate aim was to keep Riley in Norman long enough to make him the successor for the day when Stoops retired.

That day came sooner than anyone could have predicted.

The week before announcing his retirement, Stoops told Riley that he was considering it.

"I figured for him to bring it up, it was fairly serious," Riley said. "But you just never know with things like that. I really didn't know what route he was going to go."

When June 7 began, Riley still didn't.

"You knew there were some discussions, but it's just hard to nail down that it's really happening," Riley said. "Something that big, you just -- I don't know if I would've bet either way."

But a little before noon -- just six hours before the Sooners would hold a news conference to announce their next head coach -- Riley received a call from Oklahoma athletic director Joe Castiglione, who asked Riley to come to his office.

As he made his way there, Riley realized what was about to happen.

"[Castiglione] told me for sure that's what Bob was doing," Riley said. "And making sure that I wanted the job, which, that was a pretty easy decision."

From Castiglione's office, president David Boren called Riley to congratulate him as well.

"[Boren] was great, just real supportive, real excited," Riley said. "Making it clear that [Stoops'] timeline didn't have anything to do with their choice. They were all-in with me, that I had their support."

Surprisingly, Oklahoma's run to the softball title played a role in Stoops' retirement plans. Sarah Phipps/The Oklahoman via AP

Anxious with the news, Riley immediately phoned his wife, Caitlin.

"She was nervous, excited, anxious all that at the same time," Riley said of his wife, who was at a water park with their daughters. "But it wasn't like we had the long talk. It was like, you've got to get here, get my suit here, get the girls here now."

Riley also wanted to get his parents to Norman from Muleshoe, Texas, before the announcement. As it turned out, there wasn't enough time.

The night before, on June 6, the Oklahoma softball team had come back from two runs down to defeat Florida in Game 2 of the Women's College World Series in Oklahoma City and win a second consecutive national championship.

During his years in Norman, Stoops had become a fan of the school's other teams; two weeks earlier, he watched virtually every hole on TV of Oklahoma's golf championship. Stoops also evolved into a sounding board for Oklahoma's other coaches, no one more so than for softball coach Patty Gasso.

"We all felt his support," said Gasso, who would even bring softball recruits by Stoops' office, sometimes even on Saturday mornings before games. "He's been very instrumental for me, allowing me to pick his brain, giving me great advice."

Stoops didn't want to overshadow the softball team, so the original plan was to announce the retirement Friday.

By midday Wednesday, June 7, the list of people on campus who knew was short: Riley, Stoops, Castiglione, Boren, McMillen, associate athletic directors Larry Naifeh and Kenny Mossman, longtime assistant Cale Gundy, and defensive coordinator Mike Stoops, whom Bob Stoops had confided in two weeks prior in a phone call while Mike was on a recruiting trip in Dallas.

"It was hard for me to keep it [secret]," Mike said. "I couldn't talk to anybody, because I didn't want [it to get out]. It was weird."

Things only got weirder when the youngest Stoops brother (and Kentucky coach), Mark Stoops, called Mike on June 6 shortly after Stoops informed him he was retiring. During their conversation, neither Mike nor Mark knew for sure what the other knew.

"[Mark] said, 'Is Bob OK?" Mike recalled. "I said, 'Yeah, Bob is fine, what do you mean?' But he didn't tell me [Bob] had told him.

"I found out later [Bob] had, so I called him back said, 'Why didn't you tell me you knew?'"

Mark was so shocked when Stoops first called, he had to walk out of his office to the practice fields to finish the conversation.

"One of those moments you won't forget," he said, "because ... it came out of the blue."

Back in Castiglione's office, while he was still going over the job with Riley, Castiglione learned word of Stoops' retirement was beginning to get out. So they bumped up the announcement to that evening. And a text was sent to the players to be at the football building by 5:30.

Elsewhere at the stadium, it was business as usual. The Sooners were holding a recruiting camp on the field, which is where most of the assistants were, mostly unaware a seismic shift was taking place.

Stoops and Riley wanted to be the first to tell them and the players.

"We had a couple players in classes," Riley said. "We were trying to get the players over. That was our No. 1 thing, to tell them before the media. It was a race to get to them."

The team meeting was moved up another two hours, but not long after, a news conference for 5:30 was called. Stoops and Riley, meanwhile, decided to call in quarterback Baker Mayfield ahead of time.

"I was getting text messages from my friends back at home, saying, 'What's going on up there?' I had no idea," Mayfield said. "I quickly found out after that, so I knew going in that was why. But I truly couldn't wrap my fingers around it until I heard it come out of [Stoops'] mouth. ... it caught me off guard, because he's all I've ever knew of OU football."

Because of the unique summer timing of the announcement, rumors swirled that Stoops might have suffered a health scare. Yet according to Stoops and several of those close to him, there was no smoking gun, including any health scare, that prompted him to retire.

"After this long, there isn't any right way or perfect time," Stoops said. "The only other way is you're losing. ... and you get run out of town."

Oklahoma was able to make a smooth transition to Lincoln Riley as Stoops' replacement. Sue Ogrocki/AP

Stoops waited until the summer because that's when he ultimately determined he was ready. Going from the season to the bowl to recruiting to signing day to spring practice, he had little time to reflect. Stoops also faced one of the most tumultuous periods of his career in December, after surveillance video of Oklahoma running back Joe Mixon punching a female student 2½ years ago was released. After the tape surfaced, Stoops was severely criticized for his 2014 decision to keep Mixon on the team after a yearlong suspension.

Finally, during a relatively quiet May, Stoops had the opportunity to truly contemplate his future.

"When it first pops up in your mind, you think you're crazy, why would you think that? Then you start realizing, when it pops up again, maybe there's a reason this is popping up," Stoops said. "But it's a process. After 18½ years, it's not something you knee-jerk react to immediately."

Stoops concluded he wanted more time with his family, which will include watching his twin sons play their senior football seasons at Norman North High School.

He wanted more time for himself, too.

"I just think he's tired," Mike Stoops said. "It just gets harder each year, to come back and do it the way you want to do it."

As he worked through his decision, Stoops gained even more peace of mind from appraising the state of the program. The Sooners would be on the short list of national championship contenders. And they had a natural successor in place in Riley.

"It was classic Bob," McMillen said. "He knows we're going to have a good team. We've got a great senior quarterback and a lot of good leadership. And he didn't want to leave the cupboard dry at all. He wanted Lincoln to have all the opportunities to have a successful first year. That's just how he is.

"For a lot of reasons, the timing was perfect."

Because he'll turn just 57 in September, Stoops is likely to be connected to virtually every major coaching job that opens in the coming years. Still, he is adamant that his coaching days are done.

"That's my intention," he said. "That's how I feel it'll be."

McMillen, however, calls it a "guarantee" that Stoops won't coach again.

"I'm being 100 percent honest with you when I tell you, I don't think he's looked back one second since he made the announcement," McMillen said. "He wants his time."

Stoops says he doesn't know how he'll feel once the season actually starts. He also doesn't know where he'll be during the Oklahoma games, though he says that won't be on the sideline. He doesn't know if he'll even be at all the games.

"It'll be very strange," he said. "I don't know how that's going to go for me. I'm a little concerned about it -- concerned about it with a chuckle.

"But I know I did the right thing for me and my family, and for the program. But it'll be different. That'll be the tough part."

Because it all happened so fast, Riley had almost no time to talk with the coaching staff before the news conference.

"It was well done, but it was hurried," said Riley, who literally tied his crimson tie as he walked to where the event was held.

Since the assistants were set to leave the next day for satellite camps in Dallas and Houston, Riley called a staff meeting that night, first to let them know they were all keeping their jobs, and second, to reveal the plan going forward.

Then, they began phoning recruits, talking to roughly 40 of them.

Riley finally arrived home after midnight, where his wife and sister- and brother-in-law, who just happened to be visiting from Lubbock, Texas, were waiting.

"We kinda decompressed a little," Riley said. "It was one of those times when you're just pure adrenaline."

Stoops, however, had already been winding down for some time at McMillen's house, where the two couples had dinner again together, then laughed and told stories into the night.

The next morning, they were all off to Florida on a trip they had moved up. For Stoops, the first day of another life.