PITTSBURGH -- Less than a week after he tested positive for COVID-19, Steelers edge rusher T.J. Watt was activated from the reserve/COVID-19 list ahead of Sunday's game against the Baltimore Ravens.

Watt tested positive for COVID-19 on Monday and exited the protocols with a second negative test Saturday morning.

Watt's return is critical for a reeling defense that will already be without cornerback Joe Haden (foot). Defensive lineman Isaiah Buggs (ankle) and inside linebacker Robert Spillane (COVID-19) are also out, while defensive linemen Cam Heyward and Isaiahh Loudermilk missed practice Friday because of illness. Neither was given an injury designation in the final practice report, but the Steelers are monitoring each throughout the weekend.

Watt has 12.5 sacks on the season, second in the NFL behind only the Cleveland Browns' Myles Garrett (14.0).

Because he was isolated due to the league's protocols, Watt wasn't able to practice with the Steelers during the week, but he remained involved virtually and defensive coordinator Keith Butler said he prepared as if they would have Watt against the Ravens.

"I hope we have him, but we have to plan that we don't have him," Butler said Thursday. "We always have to do that. If we get him, it's a benefit for us."

Ravens coach John Harbaugh also told reporters that he was planning for the Steelers to have Watt available.

The timing gave Watt an opportunity to further rest the knee and hip injuries suffered in a tie with the Detroit Lions on Nov. 14. Watt missed the loss to the Los Angeles Chargers with the injuries but returned the next week against the Cincinnati Bengals.

Quarterback Ben Roethlisberger missed one game after he tested positive for COVID-19, returning after seven days in the protocol. Minkah Fitzpatrick and Ray-Ray McCloud also missed time on the reserve/COVID-19 list, and the Steelers still have two players -- Spillane and offensive lineman Joe Haeg -- in the protocol.