NEXT GAME

WHO: No. 3 Clemson (2-0) vs. North Carolina State (2-0)

WHEN: Thursday, 7:45 p.m.

WHERE: Carter-Finley Stadium, Raleigh, N.C.

LINE: Clemson by 13.5

TV: ESPN

CLEMSON — Not a thought hurtled through Chad Kelly’s mind. Except for the pain — oh, the searing pain.

When the anterior cruciate ligament in a human knee tears, athletes say it feels like millions of miniature balloons popping in their leg — followed by nothing. Numbness. And the long, long road ahead to recovery.

But something bizarre — mind- boggling, and perhaps even dangerous, scientifically speaking — happened less than five months after Kelly and Sam Cooper were helped off the field and into the dreaded ACL reconstructive surgery and rehabilitation process.

They played in a football game again.

Relentless rehab

Kelly is Clemson’s third-string quarterback. He was Clemson’s third-string quarterback when he scrambled during the spring game, planted his right foot the wrong way in the Death Valley turf on April 13, collided with safety Travis Blanks to the ground and … popped up immediately.

At first, nothing looked wrong. But then walking it off did no good. Kelly was done for the day, done for the summer with a knee injury that surely would sideline him for all of 2013.

Kelly is the nephew of former Buffalo Bills quarterback Jim Kelly, who joked with Chad that maybe he’d start taking after his uncle as a pocket passer to protect his legs. But that wasn’t the line from a four-time Super Bowl participant and NFL Hall of Famer that stuck with the 19-year-old.

“Doctors had told him he’d never throw a football again after his junior year in college after he tore up his shoulder,” Chad Kelly said. “Everybody knows what happened after that, so he proved a lot of people wrong.”

So Kelly swore to himself: wake up every morning and shove out the negative thoughts that plague players with an all-work, no-play rehab on the horizon. Family, friends and trainers texted him daily at 5 a.m. coaxing him to rise, shine and grind his way back.

“I knew in the back of my mind that I could come back bigger, faster, stronger and more mentally prepared,” Kelly said. “It was ‘where do I have to get to?’ This week, I’m going to get to this (checkpoint). Next week, I’m going to get to that.”

It helped that Kelly and Cooper had each other to lean on, especially for the weight room phase to regain strength in their knees. If one guy said he would do 12 reps, the other swore to do 14, and kept his word.

“One day, I was down and he was picking me up,” Kelly said. “The next day, he was down and I was picking him up.

“We were kind of battling, ‘hey, I’m coming back before you.’ Which was good. That’s what we needed.”

Taking a chance

Dr. Larry Bowman performed surgery on the pair of Tigers on May 3. A few weeks were granted to settle the swelling, and also allowed Kelly and Cooper to finish spring semester final exams.

Only Kelly’s ACL was torn. The other ligaments in his knee were spared from injury, thus simplifying the surgery (relatively, at least.)

From there, a seven-day-a-week operation of physical therapy checkpoints to build up quad and hamstring strength, providing enough dynamic flexibility to protect the knee and regain functional strength.

Outside of Clemson director of medicine Danny Poole’s training room, the road to recovery meant no running.

“ACLs used to be in a full-leg cast for six weeks,” Poole said. “You had no motion. You did nothing for six weeks.”

But doctors discovered over time that those who took the cast off themselves actually accelerated, not hindered, their rehab.

Count Kelly among the rebels. He was on crutches for two days post-surgery.

“I barely wore my brace. I was kind of not being careful,” Kelly said. “But I was careful in the sense that I’m not going to do anything stupid — I’m just going to be walking. I think that had something to do with it, that I was able to keep on strengthening it every day.”

The staff and reserves at the disposal of motivated major-college athletes, in Poole’s view, made the difference than regular civilians.

“It’s a different animal,” Poole said. “Plus, they’re dedicated, they work hard, and the result shows.”

Safety first

Kelly’s a dreamer, and a defiant young man. The same teenager whose dorm room walls are tacked with posters of luxury cars and colossal houses to remind him what NFL riches bring also can’t stand hearing the words “no, you can’t.”

Add Dr. David Geier to the naysayers. It’s nothing personal; purely in Geier’s professional opinion, five months is notoriously too soon, if not unprecedented.

“Not that it can’t be done, but it’s surprising from a biological input,” said Geier, an orthopedic surgeon and sports medicine specialist in Charleston.

“Usually before six months, that’s not good enough. That ligament isn’t strong enough to provide a stable knee, regardless of how hard somebody worked.”

Both Poole and Geier point out that skill position players — receivers, running backs and mobile quarterbacks — must regain full strength to their knee, because their livelihood is running, stopping, planting, cutting and redirecting.

The burning question: are football players who push it in five months rather than let time work for them risking their bodies?

“Yes. Absolutely,” Geier said. “The re-injury rate is higher, the earlier you go back.”

About 5 percent of reconstructed ACLs are reinjured in the first year. That rate rises for those who attempt a comeback a month or two before they medically should.

“But how much higher,” Geier acknowledged, “is the question. It’s hard to really know as a surgeon where any athlete is in that risk percent.”

The other concern is setbacks, or lack of ability. Chicago Bulls guard Derrick Rose’s mysteriously long recovery kept him out all last season, and now Washington Redskins quarterback Robert Griffin III is facing questions about an early sophomore slump and whether he returned from ACL recovery too soon.

“I don’t know why that’s happened,” Poole said. “I know what we do, and I feel really good about our rehab process. We’re aggressive with it, but we’ve got a protocol in place that we follow — until they’ve got a certain amount of strength, we don’t let them run outside. Until they reach certain goals, they can’t do cutting.

“We’ve got a way to get them from Point A to Point B, and some people take longer than others.”

Role players

Kelly and Cooper are no comparison to superstars Rose and Griffin. Cooper is one of four Tigers tight ends in the mix, and Kelly will only see the field again in sheer blowouts or if starter Tajh Boyd and backup Cole Stoudt both go down.

Their role is twofold: moral support for teammates, and taking time during the week to continue building lower body strength to avoid the pitfalls Geier cautions against.

If nothing else, Kelly was his usual passionate self in explaining exactly why he felt the need to return as quickly as he did, with zero pressure to take over the starting quarterback spot from the All-American Boyd.

“Could have taken a whole year off. It wasn’t my mindset. I love football too much,” Kelly said. “Knowing that I can be one play away from, it could be my team — I’m going to get back.”

The greatest glory Kelly and Cooper may experience this year happened a week and a half before fall camp. Barely more than three months after suffering an athlete’s worst nightmare, they went for a run on that same Memorial Stadium field.

“The coaches are upstairs on the fourth floor, and they see us run. They come out and start yelling, ‘yeah let’s go!,’ ” Kelly recalled.

“That gave me so much more motivation. I was like, this is sweet.”