When the Philadelphia Eagles hired Chip Kelly away from Oregon in January 2013, they thought they were getting a coach who’d field an innovative offense run at a madcap pace. What they probably didn’t realize, and what the rest of the league surely didn’t know, was that they were also getting a coach who intended to rethink much about how NFL teams operate, from huddling (why bother?), to traditional practices (too much wasted time), to player nutrition habits (bye-bye, Andy Reid’s Fast Food Fridays).

If they didn’t realize this, they should have, because Kelly has always challenged the status quo. “I was probably a pain in the ass as a little kid,” Kelly said recently. “I questioned everything. I’ve always been a why guy, trying to figure out why things happen and what they are and just curious about it from that standpoint.”

The result of all of that questioning was a successful debut season for Kelly, whose Eagles went 10-6 and won the NFC East one year after going 4-12 under Reid. And they did so thanks largely to approaching things just a little differently from the rest of a league that largely likes to leave well enough alone. But the NFL has a conflicted relationship with new concepts, as defiance often gives way to rapid-fire assimilation. And unsurprisingly, that’s already happening with Kelly’s ideas.

So far, most of the attention surrounding Kelly has centered on his spread offense, particularly the way in which he gives his quarterbacks multiple run, keep, or pass options on the same play, all from a no-huddle, up-tempo pace. And those ideas are certainly having an impact. The Dolphins hired Kelly’s quarterbacks coach, Billy Lazor, to implement a version of Kelly’s scheme in Miami; the league in general is trending toward more no-huddle; and several NFL coaches have told me their teams will be using “Chip Kelly plays” this season.

But Kelly’s influence extends far beyond read-options and the no-huddle, and into the subtler and more fundamental aspects of the game. In just one year, Kelly’s question-everything approach has caused many smart NFL coaches and executives to ask themselves why they’ve been doing things the same way for so long. And many are realizing that Kelly has better answers.

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It’s hard to get a first down in the NFL. The defenders are fast, the tactics are sophisticated, and the state-of-the art technology and exhaustive scouting reports mean there are no secrets. What’s innovative one week is passé the next. As a result, modern NFL game planning is an arms race of minutiae, with coaches sleeping on couches and sifting through hours of film in an effort to find even the smallest advantages.

Over the last 25 years, however, there have been increasingly diminishing returns on spending 35 hours a week engineering a situation in which there’s a 41 percent chance that a receiver who runs a 4.43 40 will match up against a cornerback who runs a 4.47 on a seven-yard route. NFL offenses have begun changing drastically in the last few years to find a better way, and Kelly’s teams have been at the forefront of that evolution, first at Oregon and now in the NFL.

Now that Kelly’s Eagles have found success — they led the NFL in rushing and yards per carry and finished second in total offense in 2013 — the conversation has shifted away from whether his offense would work in the NFL to whether that success is sustainable, and particularly whether defenses will have figured out the attack over the offseason. This line of questioning misses the mark, however: Kelly’s offense isn’t unique because of specific schemes; it’s unique because of how he organizes and implements them.

“I’ve said it since day one: We don’t do anything revolutionary offensively,” Kelly said recently. “We run inside zone, we run outside zone, we run a sweep play, we run a power play. We’ve got a five-step [passing] game, we’ve got a three-step game, we run some screens. We’re not doing anything that’s never been done before in football.”

Instead of drawing up a new play to get that one-on-one matchup for that seven-yard pass, Kelly, like some football hacker, is attacking the very logic of defenses by deploying two-on-one, three-on-two, and four-on-three advantages, whether in run-blocking schemes or pass patterns. This is why the Eagles led the NFL in plays of more than 20 yards last season. Kelly is actually trying to break defenses.

Take, for example, Philadelphia’s 2013 season opener. Before the game, Washington defensive coordinator Jim Haslett said he’d watched not only the Eagles’ preseason games, but also “23, 24 Oregon films.” He thought he’d seen it all. He hadn’t.

Early in the game, Kelly identified a particular weakness for Washington: an inability to properly defend Philly’s “unbalanced” offensive line sets. Throughout last season, Kelly frequently put offensive tackles Jason Peters and Lane Johnson to the same side while keeping only the offensive guard and a tight end on the other. And in that Week 1 contest, which the Eagles won 33-27, the Redskins repeatedly failed to account for interior gaps when the Eagles went unbalanced.

As bad as Washington’s defense was last season, few opponents fared much better against the Eagles’ unbalanced sets, which remained a key part of Philadelphia’s offense throughout the season, with Kelly continually devising new iterations, particularly on the sweep.

Kelly’s sweep is an updated version of a football classic: the old Green Bay Packers Vince Lombardi sweep, but with a particular wrinkle — a pulling center who’d lead the way for the runner. By the end of last season, the copycats had already sprouted, with the Chargers and Broncos running Kelly’s version of the sweep. Philadelphia running back LeSean McCoy delivered numerous huge runs on this play, and the Eagles ran it three times on the game-winning drive in their Week 17, division-clinching win against Dallas. The best example of Kelly’s take on the Lombardi sweep, however, came against Lombardi’s old team.

“We’re in two tight ends on this [left] side, so there’s concerns from a passing standpoint, but we have two tackles to the other side,” Kelly explained after the game. “With two tight ends to the left, the secondary support is on that side, so there’s no secondary [run] support to [the right] side.” In other words, because defenses try to match the “strength” of an offense’s formation, Green Bay’s safeties followed the tight end and wide receiver left, which gave the Eagles a numbers advantage to the right: four blockers to handle just three defenders.

This breakdown occurred not because Packers defensive coordinator Dom Capers doesn’t know how to match up against an unbalanced set. (He does. I think.) It happened because, against Kelly’s offense, it doesn’t matter what the other coaches know. The 11 defenders on the field need to be able to identify the unbalanced set and call the right adjustments, on the fly, at a super-fast tempo, while worrying about 50 other things.

“Through our formations and adjustment, we want the defense to show us how they are adjusting and playing us. We may go unbalanced or use motion to make the defense adjust,” Mark Helfrich, Kelly’s offensive coordinator and successor at Oregon said at a coaching clinic in 2013. “Early in a game we want to show things we saw on film and watch the defensive adjustments. Defenses do not have time to adjust too much when you push the tempo. What the quarterback sees is what he generally gets.”

With Kelly, it’s usually about more than what we see. What makes him so interesting is his ability to seamlessly mesh old-school tactics and NFL-style attention to detail with an approach that attacks the very structure of defenses. College football has produced a lot of innovation over the last 10 years or so, but many of the great college innovators lack the attention to detail to succeed in the NFL. At the same time, many NFL coaches are too ingrained in the old ways to adapt to an evolving game. Kelly has always been at home blending the old and the new. That’s where the NFL is going, but Kelly is already there.

Despite his reputation for both innovation and secrecy, Kelly is surprisingly open about his X’s and O’s. He even participated in a series of videos for the Eagles’ team website last season in which he candidly explained specific plays and the strategies behind them. But there are two subjects he refuses to openly discuss: his no-huddle communication system and the particulars of how the Eagles use sports science.

The former makes sense: Why would Kelly give out his signals so that opponents could steal them? Kelly’s secrecy over his team’s sports performance and recovery methods, however, points to his belief in the powerful competitive advantage that sports science provides.

From top to bottom in the Eagles organization, the first rule of sports science seems to be “Don’t talk about sports science.” Despite the limited information at our disposal, however, here’s what we know:

• While coaching at Oregon, Kelly began investing significantly in sports science, both by bringing in outside consultants and by developing in-house expertise and technology. He built principally on research first conducted for Australian-rules football.

• Many of those studies, which have since been expanded to cover a range of sports, used heart rate, GPS, accelerometers, and gyroscope monitors worn by players in practice to determine how to train for peak game-day performance and how to prevent injuries. These studies also tracked the movements that players made in games so teams could mold practices and training to what players did on an individualized and position-by-position basis.

• When Kelly arrived in Philadelphia, the Eagles invested huge sums into their sports science infrastructure, and Kelly hired Shaun Huls, a sports science coordinator who’d worked for the Navy Special Warfare Command for nearly five years, training SEALs and focusing on reducing the incidence of their noncombat injuries.

• Kelly’s team uses the latest wearable player-tracking technology, and his staff monitors the resulting data in real time to determine how players should train and when they become injury risks. “On an individualized basis we may back off,” Kelly said recently. “We may take [tight end] Brent Celek out of a team period on a Tuesday afternoon and just say, because of the scientific data we have on him, ‘We may need to give Brent a little bit of a rest.’ We monitor them very closely.”

• At least so far, it’s worked. In addition to their on-field success, the Eagles were also the second-least-injured team in the NFL last season, according to Football Outsiders.

• Just as important, the players think it works. “What happened with our players is all of a sudden when we started to get to game day every week they were like, ‘Wow, I’ve never felt this good,’” said Kelly. “And I know every guy, to a man, in December — Todd Herremans, DeMeco Ryans, Trent Cole, guys who’ve been around a long time — said I’ve never felt this great in December.”

Of course, other NFL teams have begun using sports science, and every NFL team can afford to buy the same equipment and hire the same Australian rules consultants to churn out similar data. But there’s a difference between having the data and knowing what to do with it, and Kelly and his inner circle have years of experience analyzing performance information for football. This is why Kelly is so tight-lipped: He knows that, eventually, other teams will catch up. But he’s not going to help them get there.

Kelly makes the most practical use of his research where players spend the vast majority of their time: in training and at practice. By this point, it’s common knowledge that Eagles practices are the most unique in the league: They feature blaring music (the team kicked off training camp by playing “Return of the Mack” over the loudspeakers), weird contraptions, and passing drills with every quarterback dropping back and throwing simultaneously. When Kelly took over, many commentators, former players, and coaches wondered whether his frenzied practices and up-tempo style in games would wear down his own players, particularly the veterans. Kelly, always one step ahead, accounts for this in his practice design and real-time workload monitoring.

Yet Kelly’s practices are also frenetic because he believes that’s the best way for his players to learn. “When we teach, we implement it in the classroom. We talk about what we are putting in that day,” he explained at a coaching clinic in 2011. “After that, we go to the practice field and do it. The practice field is not where we talk. It is where we do the skills. We want to keep the words there to a minimum. The words you do use must have meaning. [Players] do not want to hear you give a 10-minute clinic in the middle of the field.”

Kelly’s chief commitment isn’t to running a no-huddle offense; his goal is for the Eagles to be a no-huddle organization. For Kelly, the benefits extend far beyond the effect on opposing defenses. “One of the benefits we have from practice and the no-huddle offense, where every period is no-huddle, is our second and third [teams] — and I’ve gone back and charted this — get almost twice as many reps as other teams I’ve been at when you’re sitting in the second or third spot,” explained Eagles defensive coordinator Billy Davis, a longtime NFL veteran. That has a recruiting benefit when it comes to attracting backup players, which in turn helps the Eagles discover hidden gems. “If you’re [second or third string], you want to be in our camp because you get more reps than anyone else,” said Kelly. “Because of the reps we get in practice, our guys get a chance to develop a little more. You go to some teams and the threes aren’t getting many reps — they are losing time compared to our guys.”

The Eagles are different in how they practice, and also in when they practice: On the day before games, Kelly’s Eagles conduct a full-speed, up-tempo practice, rather than the leisurely walk-throughs run by essentially every other team in the league. “Through our research, through science, [we learned] that you need to get the body moving if you’re going to be playing,” Kelly explained. “We used the same formula at Oregon and I spent a lot of time on how to go about it, how we think you should train, and it worked for us there and it worked for us here.”

Specifically, while at Oregon, Kelly visited with trainers of elite Olympic athletes, and those trainers balked at the idea of doing next to nothing physically taxing in the 48 hours prior to competing. Kelly switched his approach and began conducting full-speed practice the day before games, and the results speak for themselves.

No NFL team practices more efficiently than the Eagles, and it’s these little details that accumulate to help Kelly achieve big advantages in the untapped peak performance arena. Doing anything that much better, especially something as fundamental as practice, will eventually spawn copycats. And sure enough, following the 2011 collective bargaining agreement, which puts significant limits on the number and length of organized practices, other teams have been forced to play catch-up to methods Kelly has been using for years.

Shortly after Kelly took the Eagles job, one Oregon staff member gave me his read on Kelly: “What people think Bill Belichick is like — thinks about football nonstop, all day, every day — is how Chip actually is. He’s a bachelor and has no kids. Football is what he’s about.” Focusing on football so completely, and questioning everything about the game, can’t be the most peaceful way to live. But that’s how Kelly’s wired. He once told a room full of high school coaches — who were eager to hear his wisdom on how to coach the spread offense and draw up cool plays — that it “bothers” him when he visits a high school practice and sees “the coaches are standing around talking to one another or throwing the ball around” while the team is stretching. Kelly’s sense of humor is well documented, but when it comes to football, he’s all business.

He knows his business is never finished. “I give myself a 58.8 percent,” Kelly said this spring, grading his first season as an NFL head coach. “That’s winning 10 games out of 17.” Kelly knows that if his team stumbles, he’ll quickly stop being “Chip Kelly, successful innovator” and become “Chip Kelly, latest college coach to fail in the NFL.” And he knows there’s always another question to ask, another long-accepted belief to challenge.

Regardless of what happens in 2014 and beyond, Kelly has already sparked change that will outlast whatever his tenure in Philadelphia winds up being. “Coaching is one thing and one thing only: It is creating an environment so the player has an opportunity to be successful,” Kelly told those high school coaches. “That is your job as a coach. When you teach him to do that, get out of his way.” In turning a 4-12 team into a division winner, Kelly also reminded a lot of his NFL peers of that lesson, and then showed them some new ways to act on it. Now it’s up to the rest of the league to catch up — and up to Kelly to stay one step ahead.

For more on Chip Kelly’s influence, check out Seth Wickersham’s ESPN The Magazine piece on LeSean McCoy’s growth.