Watt injured his groin in the first half of a Week 2 loss to the Las Vegas Raiders and didn't return in the second half.
"I think it was a tweak here or there and then tried to push through it," Watt said Friday, describing the injury's origin. "Just trying to be smart at the end of the day, ultimately. It's a long season."
Watt, who has three sacks and two forced fumbles this season, was a limited participant in practice all week and was listed as questionable on Friday's injury report.
"This isn't going around and playing pee wee football," Watt said. "This is playing against guys doing this for a living, so trying to be smart. At the same time, knowing your body more than anything. I felt like I did a good amount this week to leave the door open for Sunday."
The Steelers, though, shut that door Saturday.
With Watt and fellow outside linebacker Alex Highsmith (groin) out, Melvin Ingram and former undrafted free agent Jamir Jones will step into elevated roles. Jones, a Notre Dame product who initially signed with the Houston Texans in April 2020, impressed in training camp and played 15 snaps on defense last week.
"Jamir's been a spark ever since he's been here," Watt said. "I think you've seen throughout the preseason, whether it's special teams or playing as an outside backer, he's been able to provide a change of pace for us as an outside linebacker, and he plays the run really well and his pass rush is developing, too. Just continuing to see progression from him. I'm excited to see what he can bring to the table."