The team made the announcement on Monday, a day after the Steelers were embarrassed 41-10 on the road in Cincinnati.
Watt is the third high-profile member of the Steelers to go on the COVID-19 list in recent weeks. Quarterback Ben Roethlisberger and safety Minkah Fitzpatrick went into the COVID-19 protocol earlier this month.
Roethlisberger sat out practice after going onto the list on Oct. 13 and missed a tie with Detroit. He participated virtually the following week and returned to play in a loss at the Los Angeles Chargers.
Fitzpatrick did not play against the Chargers after going onto the list on Oct. 15.
Watt’s 12 1/2 sacks rank second in the NFL, but he was limited to just two tackles against Cincinnati while dealing with hip and knee injuries suffered against the Lions.
Watt’s potential absence is the latest setback for Pittsburgh’s reeling defense. Veteran defensive linemen Tyson Alualu and Stephon Tuitt are out with injuries and inside linebacker Robert Spillane left on Sunday with a knee injury and did not return.
The Steelers host AFC North-leading Baltimore (8-3) next Sunday.