Joe Thomas' most important trait as a legendary football player had nothing to do with his gargantuan physical abilities or his elite knowledge of the game.

Sure, he might've always been one of the biggest players on the field. He rarely lost a battle with an opposing defender unlucky enough to line up opposite of him at left tackle. He also knew what move a defender could do on each play. He rarely got beat. He's Joe Thomas, one of the best offensive linemen to ever play football.

But those skills were refined by another source of motivation. Thomas always had something else on his mind that made him want to push harder, take that extra rep or watch that last play on film.

That trait was doubt.

He had plenty of it. Ever since he took his first snap in seventh grade as an oversized youth player in Wisconsin, Thomas was always aware of how dangerous it could be to perform below expectations. 

In his mind, one bad game could ruin his football future. No, one bad quarter. Actually, it could all be derailed on one poor play.

"As the expectations go up," Thomas said in a recent Club 46 interview with Jay Crawford, "you have more self-doubt."

The expectations were always going up for Thomas, who was the top offensive lineman on the board at the 2007 NFL draft. He had an illustrious career at Wisconsin, where he recovered from a torn ACL in the final game of his junior season and used a stellar senior year to prove to NFL general managers he could be a cornerstone offensive player by simply writing his name on a draft card.

But the high expectations made Thomas nervous. He never wanted to disappoint anyone. 

That's why he went fishing on the day of the NFL draft.

"It just wasn't interesting to me to be in the spotlight like that," Thomas said. "I talked as little as possible. I didn't want to think about that stuff."

He didn't care about possible endorsements he could receive from being a high draft pick. He didn't care about putting his face on TV so that he could instantly become the next best-known man in whichever city selected him. He didn't care about looking good in a suit, either.

"I was going to be a football player," he said, "and last time I checked, we didn't need suits to go do our jobs."

So he went fishing. He drifted out with his dad, father-in-law and friend on a boat, kept his cellphone in his pocket and set up a camera to appease NFL Network, who wanted to document his draft day experience. Thomas told them he did not want them to film his live reaction.

The doubt was creeping in. What if he slid on draft day? What if all the hype was false? What if he actually wasn't the top offensive lineman in the draft?

To Thomas, those worries wouldn't enter his mind if he was on a fishing boat in Lake Michigan.

"I think it was trying to protect my own fragile emotions at that point," he said. "If something bad happens, I don't want to have to share that sorrow with all my friends and family or with a bunch of people I don't know in a place that I'm not comfortable being."

The phone rang shortly into his fishing trip. Browns GM Phil Savage was on the other end of the line. He was welcoming Thomas to Cleveland as the third overall pick of the draft.

Thomas' boat rocked around the water as he celebrated with his dad. But as the excitement wore off, the doubt crept back into Thomas' mind.

Expectations for him were higher than the Key Tower. He was expected to become an All-Pro player in a franchise that lacked them since it was brought back to the NFL in 1999. One misstep, and he'd prepare for an exit from Cleveland that would feel colder than a windy January evening on Euclid Avenue.

"I knew everybody was going to be gunning for me," he said. "The stakes were even higher, and the microscope was going to be further on me and my position. One little bad play, and the people that weren't cheering in the bar when they drafted me were going to be the ones saying, 'See, this is why I didn't want them to draft this guy.'"

Thomas ensured that sentence was never uttered. He earned a trip to the Pro Bowl in his rookie season after excelling against some of the best pass rushers in the game. James Harrison, Jason Taylor and Mario Williams — all Pro Bowl players — were all met with stiff force from Thomas, who was quickly becoming the best left tackle in the NFL.

His Pro Bowl appearances continued for the next 10 seasons. He met the All-Pro expectations, too, and earned six of them in seven seasons from 2009-2014. But the greatest accomplishment of his career was still in progress.

No NFL player likely will ever top Thomas' streak of 10,363 consecutive snaps. The monumental feat always will be his hallmark NFL achievement and perfectly encapsulates what Thomas meant to the city of Cleveland.

He did it all despite playing through arguably one of the most difficult stretches ever endured from an NFL franchise. He played with the Browns through 128 losses, no playoff wins and dealt with an always-changing combination of starting quarterbacks and head coaches. 

He never quit. He always played through any pain. He gave his heart to Browns football, and the Browns did their best to give him success in return.

"It's 10 and a half years without breaking a shoelace, having a shoe fall off or losing a chin strap," Thomas said. "To me, that is a symbol of my commitment to my teammates and how important it was for me to be on that field — through rain, through snow, through injury —  to be out there to help them because that's what the offensive line position really is about. It's about me trying to help those guys do their jobs."

Even during that streak, Thomas always had doubt. His legacy could end on a moment's notice, and nothing scared him more than disappointing the fans of Cleveland, any of the six coaches he played under or himself. 

But he knew he wouldn't disappoint anyone in 2017. That was when he called it quits after 11 illustrious NFL seasons. He felt pain in his knee all year and knew that his streak wasn't likely to continue. When he suffered a triceps injury in Week 7, he needed to call it quits. His body had tapped out.

He wasn't devastated, though. He was at peace. He had given his all to the Browns. But his body was giving him a message: His time was over.

"When that happened, it was almost like a relief," he said. "There's no question that I can continue. It gave me almost a little bit of relief because it was like a clean ending and I kind of knew in the back of my head like, that's probably the last play of my football career and I'm OK with it."

The doubt Thomas used to motivate him throughout his ironclad career was gone. He was done suppressing any worries about his performance. He had already established himself as arguably the greatest player to ever don a Browns uniform. No one needed to be convinced of his talents — not even himself.

Thomas is still doubt-free three years after his retirement. He'll always be hailed as one of the most dedicated football players in Cleveland history, and stories of his career will be passed on for generations. 

But he still has one more career milestone to check off. His name will be on the 2023 Hall of Fame ballot, which almost always brings some shred of nervous doubt to players as they await to see if they're granted football immortality in Canton. 

Will Thomas feel any doubt then?

"I don't have to worry about it," he said. "The hay is in the barn."