The news was expected after Watt suffered a Grade 2 MCL sprain, considered a multi-week injury, but the expectation doesn't soften the blow.
"Playing without T.J. is significant," Tomlin said to reporters on Tuesday. "But to be quite honest with you we've played without a lot of people this year, it's just another opportunity for us to strike a blow for the team.
"It's going to be a committee approach. We better strengthen our output in other areas because T.J. is one of a kind."
Watt led the NFL with 19 sacks in 2023, leading the league for the third time in his career. The edge beast also finished with the most QB hits (36).
Facing a surging Bills squad sans Watt will be a tall task for Tomlin's club, but the Steelers could be getting star safety Minkah Fitzpatrick (knee) back. Tomlin noted that Fitzpatrick will be limited in practice, but he's optimistic the safety will be able to play.
On the offensive side, Tomlin will continue to ride with Mason Rudolph under center, sticking with the hot hand after the QB led the Steelers to three straight wins to close the season.
Tomlin noted he wanted to "not disrupt the apple cart" after the offense found success under Rudolph.
In three starts, Rudolph has completed 74.65% of his passes for 716 yards and three touchdowns. Rudolph's three passing touchdowns of 60-plus yards in 2023 are tied for second in the NFL with C.J. Stroud. Only Tua Tagovailoa (four) has more such TDs in 2023.
Pittsburgh will need another big day from Rudolph and the offense to upset the Bills without Watt.