"I can't put a solid start date on when I can play," Watt, who has never missed a regular-season game in his first five seasons with the Texans, said. "I don't plan on missing my first game, but I can't promise it. I'm doing everything I can to protect my body, but the older I get, the more I realize you have to be smart."
Watt had surgery on July 20 to repair a herniated disk in his back. His comments at Sunday's first day of training camp were his first since the procedure, which sources have said could sideline him for six to 10 weeks and potentially jeopardize his availability for the early part of Houston's 2016 schedule.
"Last season I had a herniated disk in my back," Watt said. "But it wasn't a terrible herniation, so obviously I could keep playing. And then throughout the offseason, there would be slight flare-ups here and there, but we'd always get it under control. So it was nothing really bad.
"Right before training camp, we wanted to do a checkup and just to make sure and see where I was at," he added. "Once the MRI came back, that's when we realized it was worse than we thought. That's when we knew, and that's why it happened so close to training camp.
"It's not because it's 90 degrees and I just didn't feel like being out there," Watt quipped.
Watt, the AP's Defensive Player of the Year in 2014 and 2015 with a combined 38 sacks, said the surgery was a success.
"We took a whole bunch of junk out of my back, so now I feel good," Watt said of the procedure, which removed the herniated disk. "For the first two weeks, [the doctor] told me to just walk and lay down. That's my rehab. That's all I've been doing. But they said as soon as the two weeks are up, I can ramp up quickly."
Watt, who said he couldn't recall the specific name of the surgery, said initially hearing the recommendation was difficult.
"It was tough. It's one of those phone calls you don't want to get. But it's going to be the best for me in the long run. It's one of those things where I'm glad we found it, because if we didn't, it could've been a whole lot worse," he said.
"The fact that we're getting it taken care of now and I'm going to be healthy for the season -- that's what matters most."
Watt missed most of Houston's training camp in 2012, his second season with the Texans, and said he would draw on that experience during his recovery.
"In 2012 I missed all of training camp and didn't have a problem there, so I don't see this being a problem," Watt said.
Watt appeared to be feeling well at Sunday's first day of training camp. While he remains on the physically unable to perform list, coach Bill O'Brien said Watt is "progressing well" and remains "right on track" with his projected recovery.
The 4,660 fans at NRG Park didn't expect to see Watt, who jogged to the field about midway through the team's practice. Naturally, the unexpected good news earned him a lengthy ovation. Watt watched most of the remainder of practice from the sideline, where he sat with an 8-year-old boy awaiting a heart transplant. The boy was attending Houston's camp as part of the Make-A-Wish Foundation.
"I jogged today a little bit," Watt said with a smile, referring to his entrance. "They probably weren't terribly happy to see me do that. But I feel good. That's what's crazy. I feel good, my body feels good. It's just a matter of now listening to [the doctors].
"I'll do whatever they tell me to do, just so that I'm healthy for the first game."
With stitches from the surgery still in his back, Watt said the doctors are advising him not to stand for long periods of time or sweat. Because of that, he might not be on the sidelines on Monday or Tuesday. But with Wednesday representing the two-week mark after his surgery, the stitches are expected to be removed, which will allow Watt to begin heavier activities.
"As soon as the doctors tell me it's safe for me to be on the field, I'm going to be out there," Watt said. "There's nothing that hurts me more than watching practice and not being out there."
In addition to the herniated disk, Watt also played with a broken hand and a torn groin during the 2015 season. He had surgery to fix the groin issue earlier this offseason.
"It was the roughest year of my career; there's no question," Watt said Sunday. "But that's something that comes along with playing in the NFL. You're going to put your body through the wringer. You're going to go out there and play hurt. That's just the way it goes in the league.
"I'm doing everything I can to protect my body, and the older I get, the more I realize that you have to be smart in the way you do things and you have to be conscious of your body," Watt said.
However, Watt noted that he did understand the difference between his other medical issues and the severity of back surgery.
"The back is a little bit different than any other injury," Watt said. "I've got to listen to the doctors a little bit more on this one. You can't just feel it out, because it's your spine. You've got be smart, which I'm doing."
"I'm out here with the mindset to play Week 1. If it comes Week 1 and they say I'm not ready, then I'm not ready. But my mindset is to work to play Game 1."J.J. Watt
Because of that, Watt isn't ready to give a confirmed timetable on his return.
"I'm five years into this now," Watt said of his career. "I've learned that if you end up missing a game or two in the short-term to save yourself for the long term, that's smart.
"But that's not to say I'm going to miss a game or two," he added. "I'm out here with the mindset to play Week 1. If it comes Week 1 and they say I'm not ready, then I'm not ready. But my mindset is to work to play Game 1."
For now, Watt says his focus is on helping his teammates in whatever small way that he can.
"As soon as I'm healthy enough to come out here and stand up, I will," Watt said. "I'm going to be out here helping however I can. I think it's great for the young guys to get reps because I think we have a great defensive line and a great line coach.
"We have a really good team full of great players," Watt added. "We have a lot of guys who truly enjoy being around each other. There's just a good chemistry and a good vibe around our building. I think we have a good squad and I'm not worried. I think they're going to do a great job."