CLINTON, S.C. — The man in the gray muscle shirt is wearing no whistle, and considering his approach to, well, everything, it seems unlikely he just forgot it. But as a kickoff drill begins, Kevin Kelley, the new head football coach of Presbyterian College, needs his players’ attention.

“Whistle!” Kelley announces. He wants to condition his players to react to his voice, but also: Why carry a whistle — or identify storage space for a whistle or require yourself to remember to bring a whistle to practice — when shouting the word achieves the same effect?

A kicker jogs toward a teed-up ball, drives his toe into its nose, and off it goes, dribbling across the field and bouncing high. Kelley calls this one “NBA."

There are others, but for now, the point is: no whistle. One less thing to keep track of, and Kelley is out here a cool 18 grams lighter than he would otherwise be. Same guy who sees traffic lights, urinals and even time itself as opponents to outfox. Who wears shorts every day of the year, no matter the audience or occasion, because they’re just simpler. Who eats one meal per day, he explains at great length, because it turns his body into a fat incinerator. Just look at those sculpted biceps, one of which is tattooed with Roman numerals that commemorate VIII of the IX state championships he won at an Arkansas high school.

“Whistle!”

Kelley calls it again, and now a different kicker (who also sometimes plays quarterback) lines up to attempt what Kelly calls “Slow NBA.” This time the ball, positioned on the tee at a 45-degree angle and addressed from the top, trickles toward a line of returners before its own high bounce.

The leaders of Presbyterian College, the nation’s smallest Division I school, knew Kelley was successful when it hired him in May. They also knew he is an oddity and a rebel who flouts the customs of a sport that often takes itself too seriously. Kelley is mildly famous from his high school coaching career, mostly because he refuses to punt, refuses to even practice punting, loathes the idea of it so much that for a while after arriving at Presbyterian, he wasn’t even sure he had a punter. (“I think he transferred,” he said before the season).

But Kelley’s rebellion extends far beyond fourth down. He designed his own offense, brags about the years he spent faking that he understood defense and started using analytics when that was barely a word in sports circles. He sometimes lines up three quarterbacks in the same backfield, almost always goes for two and considers the tailback pass a staple of his attack. And while most coaches rarely attempt an onside kick, Kelley does it so often that he uses three kickers to execute his many onside kick designs.

“He truly believes this is the only way to do it,” says Zack Kelley, the head coach’s son and the team’s receivers coach.

Which is why, late one afternoon in the rural South, this seems less like a midweek football practice than a peek inside a social experiment. The weathered field is a lab, and the proctor is a mad scientist who may hold the key to the future of America’s game.

“Whistle!” Kelley says, and another kicker steps forward.

The time has come to unleash “Jet-Copter.” He jogs toward the ball, which is lying flat on the tee, and swings his foot into one end. It goes spinning, bouncing, fluttering unpredictably as two sides scramble forward. This time, the kicking team recovers it. Kelley charges forward to stand in the center of his new team and point toward where the football wound up, just as the coach had imagined it.

“Right there! That’s going to be just fine,” he says. “Right the frick there!”

***

Every few years, some brash new character bursts onto the scene to change football. In the 1990s, Steve Spurrier introduced the SEC, whose tradition was built on defense, to presnap reads and stunning scores. Hal Mumme followed at Kentucky with his blitz-proof “Air Raid.” And in 2009, Chip Kelly brought the no-huddle offense and sports science to Oregon. They all made a few enemies, especially among the traditionalists.

“I always looked at it that they were paying me to try to make those guys miserable, so I did my best at it,” Mumme says now. “It’s more fun than you can imagine.”

Presbyterian is no Kentucky. It’s a tiny private school in rural South Carolina — part of the Pioneer League, a conference of 11 schools that do not provide scholarships to athletes. It has struggled for two decades to keep its football program afloat. So Athletic Director Rob Acunto took notice when, reading through coaching applications last offseason, he noticed a claim that seemed almost unbelievable. In 18 seasons at Pulaski Academy near Little Rock, Kevin Kelley had won 87.8 percent of his games. The program had won six of the past seven Class 5A state championships. And perhaps more impressive than what Kelley had done was how he had done it.

Kelley, Acunto learned, had studied college football data going back decades. Eventually, he began compiling his own. Any penalty in the red zone, Kelley says, costs a team 1.48 points. The side with more 20-yard offensive plays wins 81 percent of the time. As much as he detests turnovers, sacks are just as bad; the team that allows fewer sacks wins 77 percent of the time, he says.

He came to believe that any formation but shotgun puts an offense at a disadvantage. And that practicing punts and punt returns and fake special teams plays are unforgivable wastes of time. So are bloated staff meetings and practices and stand-alone conditioning drills, so he streamlined his until, he believed, there were no wasted seconds.

But nothing set Kelley apart more than his refusal to punt, which earned him profiles in Sports Illustrated, HBO’s “Real Sports” and The Washington Post. In 16 years at Pulaski, Kelley asked his team to punt eight times.

His dedication to probabilities, which he believes eliminates impulse and emotion from decision-making, has earned Kelley attention and admirers: Bill Belichick, college and professional coaches wishing to pick his brain, the organizers of the annual Sloan Sports Analytics Conference at MIT. Friends came less readily, considering that emotion occasionally surfaced anyway. Kelley called out rivals on Twitter and, in 2015, publicly apologized after running up the score late in a state championship game.

His way was so successful, his profile growing so rapidly, that Kelley stood out even among data nerds — an iconoclast who refused to even consider another way.

“It was a good natural experiment because nobody else was doing it,” Daryl Morey, who co-founded the Sloan conference and is now the Philadelphia 76ers’ president of basketball operations, says of Kelley’s refusal to punt and other unorthodox methods. “In fact, early on, it may have been slightly detrimental to adoption because it had sort of a zealous feel instead of a ‘Hey, let’s follow the data’ feel.”

When Acunto made contact, he learned Kelley talks fast, thinks faster, and his identity can be distilled into three unshakable facts: He doesn’t curse, has never had a sip of alcohol, and he never — ever! — keeps his running back in the backfield to block. He had been at Pulaski for 24 years, had lived in Arkansas for twice that long, but, sure, yes, he was willing to talk to Acunto about Presbyterian’s opening.

Though not before Kelley asked the AD a question of his own. If Presbyterian were deep in its own territory, facing fourth-and-impossible, how would Acunto respond if Kelley went for it? Kelley says he has asked this to potential employers many times, including, he says, a Power Five head coach who showed interest a few years back in making Kelley his team’s offensive coordinator. They always demurred, saying they hoped he would rein it in a little, Kelley says. And that’s why “the top high school coach in the country,” as Belichick described Kelley last year, was still a high school coach.

So? Surrounded by fans and boosters and administrative fat cats, hungry after all these years for consistency and success, what would Acunto do?

“Kevin, I’m not the head coach,” the AD recalls saying. “I’m not going to do anything.”

***

It’s a little after lunchtime on a Monday, though Kelley hasn’t eaten since last night. A while back, Kelley began keeping data on himself. His body is more efficient, he claims, when it’s in starvation mode. He has lost nearly 50 pounds, he says, and it allows him to gorge each night on two-entree dinners and ice cream, which he speaks about in almost pious terms.

“It’s the last good thing we have,” he says.

Other than the grumbling stomach, Kelley is feeling good as Presbyterian’s quarterbacks file into his office. Film review is no burden after you hang 84 points on tiny St. Andrews University, as Kelley’s team did two days ago, with starting quarterback Ren Hefley passing for 538 yards and a Football Championship Subdivision-record 10 touchdowns.

“I’ll be honest with you: The guy doesn’t look open,” Kelley says after the group watches a play in the first quarter. “But you know what Ren’s doing? He’s doing what Coach Kelley told him. Read the corner; throw it to the other frickin’ guy.”

He clicks to the next play.

“Just do what you’re asked and trust the system,” Kelley continues, “and it usually works out.”

With the lights dimmed, it’s harder to notice how dank the office is, windowless with cinder-block walls. This is the head coach’s office, but it’s also the staff conference room and player meeting space. One side opens into a large, doorless restroom with four urinals that, because of probabilities that involve germs, Kelley won’t use.

Kelley claims that when he toured Presbyterian’s campus as part of his interview, guides drove him past the revivalist Neville Hall, the pillars of Alumni Green, the just-renovated Bailey Memorial Stadium. They skipped the decrepit athletics offices. But he is 52 now and had calculated the odds of the window closing on his chance to leap to a higher level of football. So he shrugged off the facilities, as he did the pay cut he says he took to leave Pulaski, and moved in May to begin making the place his own. In one corner of this subterranean bunker is a signed portrait of Donald Trump that, in gold Sharpie, congratulates Kelley on his 200th career win. In another are framed pages from a 2009 issue of Time magazine, which named Kelley’s spread offense an invention of the year.

He designed it in the 1990s while working as a scouting assistant at a high school in Texas. Kelley’s job was to study opposing defenses and write down which coverages they used and when. The problem was, Kelley couldn’t tell cover-four from a zero-blitz. He hadn’t played college football, and after graduating, he had taken jobs at a clothing store and a golf shop. So when he fell into the coaching business, he says, he mostly doodled until another coach identified the defensive alignment. Then he wrote down that colleague’s observations and, in meetings later, relayed it as his own. This went on for years, he says.

Lacking a traditional pedigree, he spent free time drawing up offensive plays that made sense to him, if only to him. He would split a quarterback out wide, removing a defender from the center of the field to account for him or, better yet, have three quarterbacks in the same backfield, confusing opponents and forcing defenders to account for something they had never seen. Receivers weren’t expected to stick to a route precisely as drawn; they would be given the freedom to read defenders’ movements immediately after the snap and adjust.

Eventually, Kelley learned basic defense and married that knowledge to what he had learned in studying data. Forever looking for ways to reduce sacks, he required his quarterbacks — and this scrambles the brains of even football lifers — to begin their passing motions before they knew where they would be throwing the ball. If the quarterback’s presnap evaluation is correct, Kelley has deduced, this shaves valuable milliseconds from the typical pass.

“You missed the throw,” Kelley tells Hefley after one of his 12 incomplete passes against St. Andrews. “The safety turns in right there; you got to get your hand off the ball. He’s done. Look at that: He is done. That hand should already be off the ball.”

“Yes, sir,” Hefley says.

“A tenth of a second here, two-tenths there,” he says, “is a sack every game.”

In those first weeks at Presbyterian, Zack Kelley could feel assistant coaches’ eyes glazing over. His dad wasn’t just talking about installing a highly intricate, timing-based system to a roster of 130 non-scholarship players, with a preseason schedule that included no spring or summer drills. His method is also an assault on typical football culture, muscle memory and conventional wisdom.

“The worst thing you can do is think,” Hefley, the quarterback, says in an interview later. “It’s supposed to be instinct-based, and thinking takes valuable time.”

Kelley says he wants to run his football program like Google, with a free-range staff and a mostly unscheduled workday. Though many coaches are control freaks, demanding their assistants be available for meetings around-the-clock, Presbyterian’s staff usually meets once daily. Because Kelley believes humans are capable of absorbing only so much information, he limits meetings with players to 75 minutes and practices to 1 hour 55 minutes. If his assistants don’t like it, he says, hundreds of other candidates “would take their spot in a heartbeat.”

The coach doesn’t lack for swagger. Spurrier was that way. So were Chip Kelly and Mumme. Like those coaches, Kelley is teaching new habits to a skeptical audience. He’s also trying to modernize a sport that resists change and acting like a pirate in an environment in which the coaches usually play nice and fall into line because that’s the easiest way to get the high-dollar games that pay for better facilities and ride planes to road games instead of buses.

“No,” he says, when reminded that the men who typically rule this arena like things as they are. “Now it is my arena. I’m in it. Why is it theirs?”

He smirks and says something about the traditions of football, especially the college game, being built on mythology.

“And what is mythology?” he says. “It’s untrue.”

***

About 200 miles northeast, the head coach of a different program is up late. He’s in his home office, watching game after game from Pulaski Academy.

Mike Minter coaches at Campbell University in North Carolina, but before that he was an NFL safety, and before that a defensive star at Nebraska. As much as Kevin Kelley represents where football may be headed, Minter symbolizes what it always has been.

It’s Sept. 15. Minter’s next opponent, Presbyterian, is 2-0 after a 68-3 win against Fort Lauderdale, and days ago ESPN aired a feature on the school and Kelley’s college football revolution on “College GameDay.”

Though Minter’s defensive coordinator has a complex plan to slow Presbyterian, Minter doesn’t think it feels right.

“You’re not going to trick me,” Minter recalls thinking that night. And as the hours passed — hours spent watching those multiple-QB formations, those unusual post-snap routines, that improvisation from receivers — he realized: Some of this felt familiar.

Twenty-five years ago, Minter was a junior when the Cornhuskers prepared for the Fiesta Bowl, against Florida’s no-huddle “Fun-and-Gun” offense. After six decades of mediocrity, Spurrier’s attack, built on deception and speed, had led the Gators to four conference championships in five seasons. By January 1996, second-ranked Florida was undefeated and had throttled opponents by an average of 44.5 points during the regular season.

Nebraska Coach Tom Osborne, who had been at the school since the 1960s, valued physicality more than speed, institutions over gimmickry. So the Huskers’ coaching staff geared down. A methodical, mega-basic defense: a scheme called cover-one “robber.” It held Spurrier’s mighty offense to a season-low 24 points, and afterward, as Spurrier’s team sulked, Minter was among those celebrating his team’s second consecutive national championship.

“That’s it,” Minter says he realized on that Wednesday night. “That’s when I went to sleep because I knew I had it: We’re going to be fine.”

The following Saturday against Presbyterian, Campbell’s base defense was cover-one “robber,” Minter says. When Kelley directed his offense to go for it on fourth and one, Hefley threw his first of seven interceptions. The Camels sacked him seven times and forced three fumbles. When the clock expired, the scoreboard showed a 72-0 Campbell victory.

Kelley shook his head as he walked off the sideline. Was this just the gulf between a program that hands out scholarships and one that doesn’t? Or the moment he got found out? Innovation may be thrilling, but it can also be cruel. Spurrier won his national title in 1997, but he and Chip Kelly eventually brought their methods to the NFL and failed. Mumme, who resigned at Kentucky in 2000 after a recruiting scandal, has spent the past two decades in the football hinterlands while the men who adapted his “Air Raid” — Mike Leach, Lincoln Riley and Kliff Kingsbury — got rich bringing it to the mainstream.

Arriving at midfield, the two coaches shook hands, and Kelley told Minter he had no idea what just happened. Then he turned to rejoin his team.

“Football,” Minter would say later, “cannot be hacked.”

***

After practice one day, Kelley drives his pickup through his new hometown, trying to make it to Fiesta Grande a few milliseconds faster than he did last time. He hasn’t eaten in 24 hours, so when he slides into a booth, he orders a taco dinner with a side of tacos.

“This job is killing me,” he says.

The week after losing to Campbell, Presbyterian lost to Dayton, 63-43, dropping it to 2-2 and choking out much of Kelley’s typical bluster. But that’s not the worst of it. Dayton went on a seven-sack rampage, the coach’s nightmare, and in his desperation he assigned his running back to remain in the backfield to block, violating one of his cardinal rules. And after so many years bracing for someone else to force change on him, of trumpeting logic over sentiment, it was Kelley who had altered this fundamental part of himself.

“Emotions make you do things you wouldn’t do, change things you wouldn’t change, think things you wouldn’t think,” he says.

He stacks together two chips and plunges them into a bowl of queso.

“There’s things that are nonnegotiable for yourself — lines that you’re not going to cross,” he says. “I’m so used to winning.”

He’d spent these last few days punishing himself. Usually Kelley eats two meals on Sundays, a reward for outlasting the week, but not this time. No ice cream, because Kelley told himself he didn’t deserve it. Instead, he watched the Dayton game, again and again, making notes for 15 hours, long past Kelley’s own rule of diminishing returns. He read critical social media posts and checked in on Pulaski, his old team and old life, 4-1 and putting up 55 points a game.

Kelley, after five months as a college football coach, wondered whether he belonged. He fantasized about quitting to join another coach’s staff as an analyst.

“I’m not there yet,” he says between tacos. “But that’s what the whispers are telling me.”

This is a coach who has never failed, and as he recoils at the feeling, he’s also confronting a supercell cloud of emotions that he has trained himself to ignore, alongside the possibility that his journey, like that of many others, may end in retreat.

Then again, it’s too early to know how Presbyterian’s season will end, let alone Kelley’s experiment. There are more games on the schedule for the now 2-5 team, for better or worse, more chances to teach and tinker. After three days of misery, Kelley finally realized that.

“I’m not a complete idiot,” he says. “I made a mistake. I just decided: ‘Wait a minute, stupid, just put it right back here like you have everything else in your life and use it as motivation.’ ”

With the restaurant closing, Kelley checks the time. It’s almost 9 p.m. Time to leave. Now. He dashes toward his truck, puts it in gear and crosses the highway. Then he pulls into the drive-through of his favorite ice cream place and orders vanilla topped with Butterfinger. The clerk asks whether he wants the small one or the tall boy. Kelley takes a breath, momentarily calculating like always, and decides, of course, that it’s better to go for it.