Kent State's Dri Archer breaks away for a 79-yard touchdown run against Bowling Green. Archer ran a 4.26 40-yard dash at the NFL combine, the second-fastest time ever. Credit: Getty Images

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Forty-five pound plates are loaded onto a sled, one by one. Heat radiating off the field, prospects rip through a brisk warm-up. The Nick Winkelman soundtrack is cranked to full volume.

At EXOS in Phoenix, formerly Athletes' Performance (API), the trainer's presence booms.

During a high-impact marching drill: "Like that button at Staples! Like that (expletive) button at Staples! Get some paper clips — punch the ground!"

Explaining form to LSU's Ego Ferguson in another drill: "Imagine I'm pulling a gun out in the Old West … pop!"

Firing out of a stance: "You have to come up and hit that (expletive) wall like you mean it!"

Right here is where draft prospects bridge the gap between "40 speed" and "football speed." Every spring, this is the NFL's Great Debate. How relevant is raw, timed speed? And how different is a 40-yard dash from a play on the football field? Many players demonize the event. Many insist it's essential.

The truth is somewhere in-between. Position to position, the demands of speed vary.

At its core, football is a game of decisions processed in milliseconds. Athletes conditioned to make those decisions without blinking end up winning.

Sweat pouring from his temples, Winkelman heads back indoors. First, he stops near a different training session underway.

"Check this out," he says with a nod.

He stops, smiles and Dontari Poe, all 350 pounds of him, leaps atop a towering box from two feet. A remarkable sight. This is the same specimen who broke five seconds in the 40. Winkelman shakes his head, walks inside and takes a seat on a trainer's table.

The NFL scouting combine, he says, reveals raw, plain speed. No reaction is necessary. There's no measure of an athlete's "neuromuscular capabilities."

His mission is to simulate football speed — "40 speed" spiked with decision-making.

"What we do for the 40," he says, "is build the raw materials. If you're slow as (expletive), you're going to be slow as (expletive) on the field. But if you're fast as hell at the 40, it doesn't mean you're fast as hell on the field. And that then becomes the decision-making piece."

You need both. The NFL game is faster than ever. It's on teams this Thursday through Saturday in the NFL draft to dissect the importance of speed, position to position.

Running backs need speed

On the field, Henry Josey feels weightless, like he literally does not have pads on. It's the unapologetic "track speed" in him. Through three surgeries, the doubt and the resurrection, this 5-foot-8, 194-pounder from the University of Missouri insists a 40-yard dash reflects a back's speed.

"Once you get north and south," Josey said, "you go as fast as you can. That hole you have to get through is there a split-second. You blink and it could be closed. To make quick decisions, you definitely have to be able to explode through the hole as fast as you can."

He'd know.

In November 2011, Josey tore his ACL, MCL, meniscus and patellar tendon in his left knee and somehow played football again. By 2013, he rushed for 1,166 yards, 16 touchdowns and then pulled a 4.43 in the 40, third-best amongst all running backs.

His speed is triggered by that left leg. On basic zone plays, the back stretches his run wide, "presses" the hole, waits, waits and then bursts upfield. Josey holds out until the absolute last split-second to turn it up, comparing this to the always-vital start of a 40. From there, the NOS-charged speed kicks in.

Josey gets separation. He broke free for runs of 68, 45, 50, 86, 57 and 65.

In his team's 41-31 Cotton Bowl win over Oklahoma State, Josey, redirected off his left knee all game for 92 yards on 12 carries with three touchdowns. Tied up in the fourth quarter, Josey strung out a zone play left for nearly two Mississippis, cut on a dime and sped 25 yards north for a touchdown.

Speed is part nature, part nurture for Josey. In the 1990 Class 5A Texas Championships, his father broke the national high school record in the 100 meters with a time of 10.15 seconds. The record still stands. And once he was healthy, Josey did everything possible to reawaken his second gear. Soon, he was squatting more plates than ever. He danced through near-impossible cone drills that knotted teammates into pretzels. That first summer back, Josey challenged his entire team to races during workouts. Nobody ever stepped up.

Josey inherited his father's speed. He has broken 10.5 seconds himself in the 100. He simply chose to channel it into football instead.

The Dri Archer, De'Anthony Thomas, Henry Josey wheels are rare. Any 4.3 or 4.4 time should excite scouts. Winkelman calls it "getting wired."

"A Chris Johnson-type," Winkelman said. "With hardly any effort, they're gone. A lot of that has to do with — the reason we say 'wired' — is the way their nervous system is wired. If we were to look at their muscles, compared to our muscles, how their nervous system interacts with them would be different in them than us. It's more sensitive. It's more responsive."

These players, you never catch in the open field. These players can pause to redirect in the backfield.

The 230-, 240-pound running back usually can't afford to wait. They mash instead of dash. And if you run a 4.6 or 4.7 as a regular-sized back, well, good luck.

"I don't know if you will make it," Josey said, "especially going to the competition level you're going to in the NFL. Everybody's a superstar."

Not that everyone agrees.

Running backs don't need speed

Driving back from a morning workout, Ka'Deem Carey cannot stop laughing. He gets it, people. He's slow. He ran a 4.70 in the 40. Five defensive linemen ran faster times. Your neighborhood mailman might give him a push.

Carey chuckles, pauses, and then gets serious. OK. The criticism does bother him.

"They're making it seem like the 40-yard dash is why we play football," the Arizona back said. "I just don't understand that. We play football because we run the football, we pass the football, we catch the football. It's not a track meet."

At one end of the spectrum is Josey, Archer. At the other end is Carey, a 5-foot-9, 207-pound human pinball who rushed for 3,814 yards and 42 touchdowns the last two years. The coaches and scouts, he hopes, will rely on the film. Not on his eyesore of a combine.

His argument is simple. A running back doesn't run in a straight line. He dodges, reacts, needs "to be on point" with reads.

"Reaction time is the best time you need," Carey said. "If somebody's chasing you, come on now. You have times faster than a 40 time. You have to get on your horse."

He admits there's no "wired" muscle fibers for him. Carey has never been the fastest on the field. Not even in high school. That's why, he says, his vision is rare. Call it basic survival of the fittest. Carey was forced to adapt to a shortcoming.

He claims to see plays before they happen. He needs to see that cut before the Joseys do because there's no bursting through slivers of daylight. This sixth sense, Carey insists, "covers up that 40 time."

"I have to rely on something else to actually get there on time," Carey said. "I have to be smarter than the defense."

One 366-yard eruption made Carey believe his argument. One 366-yard day, Carey slowed an entire defense down to his level. The week of Arizona's game against Colorado in 2012, Rich Rodriguez told the sophomore running back to be ready. Their starting quarterback was out with a concussion. He'd be the workhorse.

So all week, Carey lived in the film room, hunting for tendencies. On tape, Carey noticed that when one Colorado linebacker moved up to the line before the snap, the back-side cut was wide open.

And that Saturday played out like a game of Madden on N64. Carey found the glitch. He knew what'd happen before each play — a cutback into a four-lane highway of nothingness. The 366 yards set a Pac-12 record. "A perfect game," Carey called it. As a slower running back in the NFL, he laughs that he better slow everybody else down.

"I was just having a field day with them," Carey said. "Everything was going right. The defense was extremely slow. I knew what they were doing before they did it."

As bad as that 40 was in Indianapolis, Carey is confident he's got "just enough" speed. Make that very confident. Carey half-jokes that the Green Bay Packers haven't expressed interest because a team with Eddie Lacy and himself would be downright "cheating."

"There isn't any media who can tell me how I can play my game the best," he said. "I know how to play football. I've been playing it since I was little. But track, 40 speed, that's different. I haven't done that. You can make that a big deal but I know my game. I'm very confident.

"Football and track speed, it does not cross paths."

Making the connection

So who's right — Carey or Josey? Back to Phoenix. Back to Winkelman's lab.

For one period, LSU's Ego Ferguson, Ohio's Travis Carrie, Texas' Carrington Byndom and others hop on one leg over low, close hurdles. They move to a nearby wall, tucked underneath a lip of shade. Hands pressed against the wall — a partner pulling on a resistance band attached to their waist — prospects must fire their knee up on Winkelman's "Hold … Hit!" command.

This then evolves into players firing up each leg in rapid-fire "Switch! Switch! Switch!" mania.

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Prospects head to the field. In a resistance harness, they tilt their bodies 45 degrees and aggressively march with a partner pulling from behind. This march then evolves into explosive, 15-yard bursts of bounding.

Most drills are conducted in tight spaces. Winkelman compares it to a game of soccer in a 10-by-10 square. Compressing the field of play forces players to be precise with each pass. So through this all at EXOS, prospects discover their "hidden muscles," the muscles that fuel football speed.

Ohio's Carrie wasn't sore his first three days in Phoenix. That fourth morning he woke up in stinging pain.

In college, the cornerback worked large muscles through Olympic lifts, power cleans, front squats and the like. Here, smaller muscles are isolated.

"Holding you leg up sounds small and simple but we tend to forget about it because it's so small and simple," Carrie said. "That increases the muscles that kind of hold everything together that we're not used to using. … You start to find those muscles and you start to feel weird that 'Man, this is an odd feeling.'"

Body. Task. Environment. Typically in training, Winkelman says, the "body" and "task" are involved. You lift a weight. You catch a football. He toys with the "environment," the variables that tend to dull raw speed in a game. He'll line up six different colored cones, have prospects shuffle back and forth at full speed and shout "Orange!" and "Red!" Prospects must grab specific cones on command and toss them aside. Each decision is timed.

In a similar drill (one cornerback Desmond Trufant conquered), prospects swipe as many flashing "lasers," gates, as they can in a 30-second span.

"A lot of guys, offensively and defensively, try to make decisions before any information has been given to them to tell them to make those decisions," Winkelman said. "We try to create an athlete who has a very open mind, who's ready to take in information."

This is how Winkelman knew Randall Cobb would be a star. Often in these drills, Winkelman sees hesitation in prospects, "speed bumps." In the Kentucky quarterback-turned-receiver, Winkelman immediately saw a 360-degree, open approach to the game. Cobb's 4.46 time in the 40 ranked 10th best at his position. Above-average. His decision-making speed would probably rank first.

Grabbing a cone. Reading a cornerback. Mid-drill or mid-play, nothing clogs Cobb's mind.

"I knew he was going to be incredible. Absolutely," Winkelman said. "There was no question."

Forty-speed is a starting point. Football speed demands decisions.

The wide receiver

All teams hunt for the prospects who eliminate the "speed bumps." Clipboards in hand, pro scouts grill receivers at the combine, in pre-draft interviews, after Senior Bowl practices in Mobile, Ala.

What did they process mentally pre-snap, post-snap?

Wyoming's Robert Herron dominated all Senior Bowl week. He ran a 4.35 at his pro day, too. Yet this is all only a thumbnail into his game. He knows speed and athleticism alone aren't enough.

"When you say 'track guys,'" Herron said, "they put on a helmet and shoulder pads and they can't move like they move on a track. … They don't know how to control their speed. You can't be going 110% always because you have to put your foot in the ground and cut."

Natural change of direction, Herron says, is embedded into his football DNA. He played running back his whole life.

Replay the bubble screen he took 93 yards for a score against San Jose State. As he caught the ball, Herron simultaneously juked a tackler inside and then looped back outside. Gone. Same story on an 82-yarder against Texas. On a short curl, he broke two tackles and instantly bounced outside to elude another. Gone.

Without those two decisions, Herron gains three and seven yards.

But the decision-making doesn't stop there, either. For receivers, the option route is crucial. At the top of a 6- or 12-yard route, a receiver must decide whether to break left, right or turn around … on the same page as the quarterback.

All spread offenses rely heavily on option routes. A hiccup of hesitation can lead to a pick-six.

For Aaron Rodgers' receivers, it takes multiple seasons — and many August scowls — to build this trust. So crisp route running can compensate for 4.6 speed. After all, Jarrett Boykin ran a lumbering 4.74 at the combine. In the last nine years of 340-plus participants, only three other wide receivers were slower.

Boykin went undrafted. He didn't even escape the Jacksonville Jaguars' rookie camp.

And there he was in Dallas schooling Brandon Carr on a back-shoulder throw for 27 yards one week and ripping away a touchdown from Pittsburgh's Cortez Allen the next. In Year 2, Boykin broke out for 681 yards and three scores in essentially 11 games. He made James Jones expendable.

Seventh-rounder Charles Johnson of 4.35 fame? He didn't play a snap in Green Bay.

Said Herron, "There are a lot of dudes who don't have the 40 speed but can play football."

Zero-to-60 acceleration still matters. Strike fear deep, Wake Forest's Michael Campanaro explains, and you instantly put a cornerback on roller skates. You take control of this decision. The comeback route, the back-shoulder, the slant all become easier.

Something like Kevin Durant drilling four straight three-pointers and then using a pump fake to get to the rim.

"Getting him to flip his hips," Campanaro said, "that's where that get-off comes into play. That's why a lot of teams look at 10-yard splits and 20-yard splits — to see how quick they're getting off the ball."

Then, off the ball, few routes stay in a straight line. That's why Campanaro is a huge fan of Pittsburgh's Antonio Brown and Cobb. Brown darts in all directions. And in Green Bay, position coach Edgar Bennett harps on technique, on "leveraging" routes. With a dip of a shoulder, a stutter step, a lull to sleep, Cobb angles corners where he wants them.

He's never drowned by the speed bumps. As Campanaro said, all receivers must know "when to be 100% full speed" during a route.

"Love Randall Cobb," he said. "He's definitely one of the top slots in the league."

The weapon

During a mini break at EXOS, Winkelman asks a question out loud to players.

"That little running back from Kent State," he says, "he ran a 4.27? Did he play that fast?"

Make that 4.26. Dri Archer is this draft's urban legend. A filthy-fast athlete without a traditional position. In the NFL, Archer can't hold up as a full-time running back, nor is he a polished receiver. In space, let loose, he might be untouchable. It's on coaches to scheme speed, too.

Kent State offensive coordinator Brian Rock noticed Archer's special speed on a recruiting trip. He was with Purdue at the time and Archer was "electric." This was the type of acceleration no trainer can mold at a training facility in Arizona.

"That speed's genetic, man," Rock said.

Said Winkelman, "A guy that fast, if he can translate that speed side to side, then it's just a question of 'does he have the decision-making capacities to do it?'"

In the Mid-American Conference, Archer did.

Rock put the ball in Archer's hands through sweeps off motion, isolated 1-on-1's, jet sweeps, pitches. Archer wasn't a mere Corvette. Archer's change of direction separated him. His body control. He was slippery. He redefined "running back" at Kent State.

"The more he touched it," Rock said, "the better off we were going to be."

Decisions may drive game speed. But the NFL is also a game of personnel mismatches. Coaches need to get their fast players on your slow players. Because of that 4.26, Archer will get a chance.

The pro game does get faster. Some ambiguously defined "offensive weapons" have struggled (Denard Robinson), some hybrids (Darren Sproles being the blueprint) have excelled. Archer and Oregon's Thomas are up next.

Rock isn't sure if the 173-pounder can withstand the NFL pounding, only saying he "wouldn't want to play against him." During Kent State's practices, Archer could embarrass a teammate at any moment.

"He can do some things that not everybody can do," Rock said. "When you have that ability to do some things, it's not so much making guys look silly. It's more everybody just looks at each other and says, 'How did he do that?'"

The safety

Given a Pop Warner mulligan, Ka'Deem Carey isn't so sure he'd choose to be a running back again. Then, it was a position of glory. Now, the position is drafted later, paid less, treated by pro teams as a walk through K Mart.

Not so for safeties. This off-season, Jairus Byrd (six years, $54 million) and Earl Thomas (four years, $40 million) received whopping contracts. Perfect timing for a guy like Florida State's Terrence Brooks.

"Earl Thomas is the standard right now at safety," Brooks said, "and everybody wants to be that type of guy."

Safety stock soars because in 2014 — with these spread offenses, alley-ooping tight ends and mad-scientist quarterbacks multiplying — playing fast on defense is more difficult than ever. Game-speed decisions at safety must be made at a 40-yard-dash rate.

The safety loiters 10-12 yards from the line, half-clueless at what's next. A period of diagnosing serves as the "clutter" Winkelman tries to minimize.

"It's way easier for offensive players because they know what they're doing," Brooks said. "They know what's going to happen on a play. But on defense, you can recognize plays but knowing exactly what somebody's going to do — that's what makes it hard to play defensive back. That's what makes us better athletes."

No wonder Brooks snuck his iPad playbook into his college lectures. He'd ignore the occasional professor to get a jump on that week's opponent.

Playing a mix of Cover 2 and deep center, no player had more ground to cover on the field than Brooks. When he's deep, his eyes typically stay on the quarterback as long as possible. Like Josey staying patient, Brooks can afford to read the quarterback because of his 4.42 speed and 38-inch vertical. Both topped the safeties at the combine.

Against N.C. State, Brooks saw the quarterback load up, flipped his hips and chased down a diving interception.

The difference between a 5.3 and 4.9 offensive guard may be minimal. The difference between a 4.7 and 4.4 safety, Brooks believes, is substantial. The safety can turn a 15-yard run into three yards with one cannon-blast close. Brooks had eight tackles for loss in 2013.

From deep, he closed on Syracuse's Tyson Gulley in 2.3 seconds. He read a jet sweep to N.C. State's Johnathan Alston, forcing a fumble in two seconds flat.

As Brooks deadpanned, "What's a safety without being fast?"

First, one must diagnose. Fast.

"Some of that comes from being a natural football player," Brooks said, "recognizing what's going on and not hesitating. Some of it comes from film study. I feel like that's where my feeling will be a lot higher than a lot of these other players."

A game of miliseconds

So the search is on for real speed. A position-by-position quest.

Green Bay surely knows it is a game of inches, of milliseconds. On its Super Bowl run, it took a shoestring tackle of DeSean Jackson and multiple thread-the-needle strikes from Rodgers to go the distance. Last January, the Packers were a split-second away, again and again and again - Morgan Burnett on Vernon Davis' touchdown, Micah Hyde on his missed pick, Jarrett Bush on a whiffed blitz.

They weren’t running 40’s in a climate-controlled environment. This was a 4-degree igloo against San Francisco. A season was on the line.

Winkelman knows one timed sprint is important, yet only tells "part of the story."

“You need that terminal piece, and the terminal piece is decision-making,” Winkelman said. “You can flood someone. If you throw someone in a game and they don’t even have baseline decision-making characteristics, that’s where they can’t see the forest from the trees. They get blinded.”

Colin Kaepernick and the San Francisco 49ers still stand in the way. Track-fast Seattle, too. Assessing the speed necessary to — once and for all — slay the dragon is no exact science.

Ted Thompson can start with a 40-yard dash. But that's only the beginning.