Watt went down with a groin injury in the second quarter and was officially ruled out after halftime. Both cornerback Joe Haden and linebacker Devin Bush also had groin injuries -- theirs sustained during Friday's practice -- that kept them out of the 26-17 loss.
In addition, Steelers wide receiver Diontae Johnson suffered a knee injury on the final play of the game, an 11-yard reception from Ben Roethlisberger, and nose tackle Tyson Alualu fractured an ankle in the first quarter, coach Mike Tomlin said, leaving him sidelined for an "extended" time.
"T.J. was raring to begin the game and had a lot of havoc early," defensive captain Cam Heyward said. "Losing Ty was definitely something we had to adjust to. It took me a while to just settle down. But, he's a heck of a player. ... Having a guy like Tyson and T.J. out there, there's almost a blanket there. We were already down [Stephon] Tuitt to start with, but it's going to have to be a collective effort. It's not one man to be Superman, but the group has to pick up the slack."
Prior to the season opener, Watt signed a four-year, $112 million extension that made him the highest-paid defender in the NFL. He didn't practice in the team periods for all of training camp and joined the Steelers for the first time four days before the Buffalo Bills game.
Before Watt's injury -- which appeared to occur early in the Raiders' final drive of the first half -- the pass-rusher had a strip-sack of quarterback Derek Carr, along with four tackles. Watt recorded his first strip-sack against Josh Allen and the Bills a week ago.
With Watt out, the Steelers (1-1) used a three-man rotation of Melvin Ingram, Alex Highsmith and former undrafted free agent Jamir Jones. Ingram got a sack in the second half, and the Steelers added four quarterback hits.
Still, it was impossible to replicate Watt's production.
"Any time you lose the best player in defensive football in the NFL, there's going to be a drop-off," said inside linebacker Robert Spillane, who started in place of the injured Bush. "There's nobody like T.J. Watt. Melvin and Alex are two very high-end outside linebackers who do a good job of getting a consistent pass rush. I know that they'll be in the lab working, getting better at their craft every day."
Alualu's injury, sustained in the first quarter, was also costly with the defensive line depth already thinned by injury. He was helped off the field by Chase Claypool and Isaiah Buggs, and was carted back to the locker room after an evaluation in the injury tent.
"That hurt," Heyward said. "To be honest with you, I wasn't ready for that. It goes back to training in the offseason together. Getting him to stick here. Him staying around. Him working his tail off. I thought Tyson was destined for one of his best seasons. I've said it before, he's the good cop to my bad cop. He settles the group down. Sometimes that can be too high or too low and he brings me back down. And he brings the team back down. I'm not going to sit here and make it a eulogy, but we're going to miss him out on the field."
In the fourth quarter, Steelers right guard Trai Turner was ejected for unsportsmanlike conduct after he appeared to spit toward a Raiders player. Turner appeared to be angry about something that occurred during a play where Najee Harris and Roethlisberger hooked up for a 25-yard catch-and-run touchdown.
Tomlin said Turner was spit on first.
"Somebody spit in his face," Tomlin said. "And so I understand the 15-yard penalties and so forth, gaining control of the game and stuff. Trai is not a young guy. He's not overly emotional. He's a flat-liner. For him to respond the way he responded, what transpired had to transpire. I was stating that case to [the officials].
"I didn't believe he did enough to be kicked out of the football game. That was just my opinion."
"From my vantage point, I saw one of their players try to spit on one of my teammates and he was charging him, so I went in there to kind of separate it and I got called for unsportsmanlike, and I thought I was separating [them]," Thomas said. "I've just got to take care of my teammates and it's just instinct out there. You never want to see another guy spit on your guys, or charge them and try to fight them. So I just wanted to make sure that he didn't touch Maxx [Crosby], or get close to him."