HOUSTON -- The signs started popping up everywhere. J.J. Watt was starting to look like his old self.

Derek Watt saw it while he was working out with his brother in Waukesha, Wisconsin, during the offseason.

Johnathan Joseph saw it when he was at the Houston Texans' practice facility in the middle of the summer and watched Watt running half-gassers -- a sprinting drill -- in less than 14 seconds.

"I know you can't run 16 of those if your knee is bothering you," Joseph said. "I knew kind of right then and there where he was headed."

Texans coach Bill O'Brien saw it during training camp, when he realized his defensive superstar was not only out on the field consistently but also practicing the way he had before his injuries.

But Watt didn't quite believe it himself.

The three-time NFL Defensive Player of the Year had missed all but eight games over the previous two seasons, sidelined first by back surgery in September 2016 and again after he broke his left leg a little more than a year later. Watt not only has stayed healthy through 10 games this season, he's playing at an extremely high level.

Entering Houston's game against Tennessee (5-5) on Monday Night Football (8:20 p.m. ET, ESPN), Watt has 10 sacks, tied for fourth on an NFL leaderboard he wasn't sure would include his name again.

"Everybody told me I was washed up," Watt said. "I don't blame anybody who didn't know if I was going to be the same again because there were times I didn't know. So, I can't sit here and get too mad at people who thought I might be washed up or thought I might be done, because I was sitting in that same boat when I was sitting at home with a cast on my leg and not being able to walk, thinking, 'Man, will I be the same again?'"

Finally, 11 weeks into his eighth NFL season, even Watt is starting to believe he has returned to form.

Long road back

Watt needed surgery hours after he shattered part of his leg, suffering a tibial plateau fracture on Oct. 8, 2017, when tackling Chiefs quarterback Alex Smith. In the weeks after his surgery, Watt wondered if his leg would ever be the same.

"You're sitting there on your couch and you're like, 'How the hell am I going to get back to where I need to be?'" he said. "You're sitting there and you can't even do a leg raise, you can't even do anything, and you're like, 'Is this possible?'"

The defensive end had to start walking again, and he did that for the first time on Dec. 1. In mid-January, he was able to run for the first time, but it wasn't until midway through the summer that he felt confident he could "push it and really test the limits."

"He was here every day at 6 a.m. [and] put a lot of time into it. I can't even imagine what he did, to be honest with you," O'Brien said. "I've never seen anything like it. To come back from what he's been able to come back from, some really serious injuries, and to be able to play at the level that he's playing at, it just says all you need to know about him."

Watt, 29, didn't let those questions linger once he could get back to work.

"Once he decided for a fact he wanted to keep playing football, the switch flipped and he was the same old guy I knew, working as hard as he could be," said Watt's brother, T.J., an outside linebacker with the Pittsburgh Steelers.

Derek Watt, a fullback for the Los Angeles Chargers, said during the time he, J.J. and T.J. trained together, he could tell his older brother was getting back to where he was before his injuries.

"He felt better than he did last year, or the year before," Derek said. "I knew it was going to be different than last year."

Most players have a strong drive to succeed -- it's hard to get to the NFL without it -- but teammates and coaches are quick to point out that Watt's desire is different.

"If you could just build a football player, you'd build J.J. Watt," Texans defensive line coach Anthony Weaver said. "And it has nothing to do with his physical attributes. It has everything to do with his mental makeup and his work ethic and his toughness. He's a coach's dream.

"There was no doubt in my mind after enduring the things that he had gone through for two years that he was going to overcome that. Because a lot of people said that he couldn't. And if you ever want J.J. to do something, just tell him that he can't do it and he'll get it done.

"Once you start seeing those small victories ... you knew he'd turn the corner."

Watt can't pinpoint the exact moment he turned that corner, but he was hopeful during his summer workouts. He played only nine snaps during the preseason, and in the first half of the Texans' season opener against the New England Patriots, he said he felt a little out of sync.

Then, in the second half, he said he started to knock the rust off. His first sack in more than two years came in Week 3 against Eli Manning and the New York Giants. He finished the game with three.

"Every week there's a new thing that you start to feel a little bit more and more like yourself," Watt said.

Since that game against the Giants, Watt has had at least one sack in every game except Week 7 against the Jacksonville Jaguars. Along with his 10 sacks this season, he has 12 tackles for loss and 17 quarterback hits.

Regaining confidence

Watt credits two groups of people for his comeback: those who doubted him, and those who gave him the confidence to return.

"It's a 'what have you done for me lately?' world. People tend to forget very quickly what you've done in the past," Watt said. "So I just want to be able to come out here and play the way I know how to play as kind of a reminder to both everybody else and myself of what I'm capable of."

Texans safety Tyrann Mathieu, who has overcome a torn ACL twice in his six-year NFL career, understands the difficulty of cultivating a persona and reputation only to see an injury derail the momentum.

"Everybody just kind of forgets about it overnight," Mathieu said. "Literally, overnight, they forget everything you've done."

Mathieu, although new to the Texans this offseason, said he made it a point to be there for Watt, because he knows how hard it is to go through the rehab process solo.

"You don't want to feel like you're alone when you're going through difficult times," Mathieu said.

"If you ever want J.J. to do something, just tell him that he can't do it, and he'll get it done." Texans defensive line coach Anthony Weaver

Since his injury, Watt has talked about the importance of those around him helping him get through his rehab. He points to his girlfriend, Houston Dash forward Kealia Ohai, who was going through a recovery of her own, from a torn ACL suffered on the soccer field. He credits his family and the Texans' training staff for helping him see what can be possible. And he is grateful for Weaver and defensive coordinator Romeo Crennel for the encouragement they provided so he could get in the right mindset to return to the field.

"Everybody helped build that confidence back up, because confidence doesn't come naturally after an injury," Watt said. "It's very, very difficult to build back up, because you're at a place where you've never really been before. You have to figure out, 'OK, how do I get back to that place?'

"There are a whole bunch of people in my life that helped mentally get me back to where I needed to be so that, physically, I could be the person I need to be on the field, too."

Watt said Crennel always made him feel he was a part of the team, even when he had to spend the majority of his time in the training room instead of the meeting room.

"Every single day when he walked past, he'd tap me on the leg, he'd ask me how it's going, we have just a little two- or three-minute conversation," Watt said. "It was, most of the time, just about nothing, but he was there every single day and he would always just ask me, 'How's it going? What's going on?' It's just little things."

Though Watt was grateful for the encouragement, Crennel was quick to point out that the veteran didn't need any motivation during his rehab process.

"When he was totally healthy, he was a workaholic anyway," Crennel said. "Then he got injured and he continued to be a workaholic because he knew that's how he would get back."

Back in form

Watt has seemingly added to his career highlight reel every week in 2018. After his three-sack performance against the Giants, he had two the following week against Colts quarterback Andrew Luck. Mathieu points to Watt's sack against the Bills, when he beat "the tight end, the tackle, then the running back" to get to quarterback Josh Allen.

"That's just the kind of play we're used to seeing him make," Mathieu said.

Watt said he doesn't worry about getting hurt again. He can't, he said, because it would change the way he plays. But every time he walks off the field, he's grateful to have made it through another game.

He might have felt rusty in September, but it didn't take long for opponents to realize the defensive end they had seen in the past was back.

"If you turn on the tape, he looks just as dominant as he did back then," Weaver said.

Watt has put himself in the conversation for what would be a record fourth NFL Defensive Player of the Year Award, but it would likely take an incredible finish and some luck because Los Angeles Rams defensive tackle Aaron Donald has been dominant.

But that's not the point. Even if Watt does not win that award, it's impressive he is even in consideration after all he's been through since he last won it in 2015.

"[It means a lot] just to be back in the game, to be back in conversations like that and to be able to go out there and perform the way I know I can perform," Watt said. "And like I've said all year long, I'm still not even there yet, but working toward being back to the player I know I can be and am, it feels good."