Jaylon Smith never wavered in his long road back from a devastating knee injury that threatened to end his professional career before it even started.

Smith was on the verge of becoming a top selection in the NFL draft. Dominant, with elite playmaking ability and natural football instincts, he was a consensus All-American at Notre Dame and 2015 Butkus Award winner as the nation’s top linebacker for a reason.

But in a matter of seconds, in his final game as a college player, Smith’s future crumbled when his knee hyperextended under him. What started with a simple shove from an Ohio State lineman resulted in a torn ACL, LCL and, most significantly, nerve damage in Smith’s left knee.

Fearful he wouldn’t recover from the nerve damage – one report stated it was 50-50 he would ever play again – teams passed on him in the 2016 draft, and the tackling machine fell all the way to the Dallas Cowboys with the 34th overall pick.

It was a seemingly devastating turn for a 20-year-old, but unlike his knee, Smith never crumbled.

“I’ve taken care of a lot of pro athletes,” Dr. Dan Cooper, the Cowboys team physician, told Yahoo Sports, “and Jaylon Smith stands out as the No. 1 person in having an unwavering positive attitude.

“I never saw Jaylon down in the dumps, never saw Jaylon without a smile on his face. He calls it the ‘clear-eyed view.’ I never saw him waver. He just stands out.”

By picking him in the second round, considered a reach at the time, Dallas was betting on Smith’s character as much as his talent, knowing full well he would have to redshirt his rookie season.

The trauma on Smith’s leg mostly impacted “his lateral movement and transitions back into [pass] coverage,” Cooper said.

Smith had a year-and-a-half of tedious daily exercises in his injury rehab, including what Cooper describes as an especially brutal first six months when mobility is equally limited and painful. Remember, this was not just a normal ACL injury. Smith hyperextended his knee, tore his ACL as well as everything on the outer side of his knee and stretched his nerve to a degree that it degenerated and caused significant atrophy, according to Cooper.

This is why Cooper came away so impressed with Smith’s mental makeup and frame of mind. He repeatedly noticed how Smith stayed the course, believing that his daily regimen would ultimately become a conduit to his full recovery.

“It’s really about the player,” Cooper said. “I do think that some medical staffs wrote him off. I think they just saw him at the very bottom. There were some [medical staffs] that were convinced he had no chance of getting it back. There were some that probably just weren’t willing to take the risk. … It was a gamble on the part of our ownership and management, for sure. But it was an educated gamble. We knew that he had probably better than a 50 percent chance of getting most of his function back.”

View photos Jaylon Smith had 81 tackles for the Dallas Cowboys last season. (Getty) More

Smith’s determination came from missing the game and a desire to be the player the Cowboys hoped he could be. There was also the fact that he never considered an alternative. Returning to the field was not merely something he wanted; returning to field was a necessity.

“I never had the opportunity to think about any type of doubt whatsoever,” Smith said, “because any type of doubt or misconception would have hindered my growth in where I am today.”

Seventeen months after being drafted, in September 2017, Smith made his professional debut. He played in all 16 games last season, starting six. As a “rookie” coming off a potentially career-threatening injury, he amassed 81 tackles, and on just 17 pass rushes, forced four hurries, two fumbles and one sack.

Despite his success, though, Smith was still not himself. He had more in his arsenal.

“I wasn’t 100 percent or even close it, but that’s no excuse,” he said. “I was out there. I learned from the bad and the good.”

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