Coach Mike Tomlin said Tuesday that McDonald has a hip issue while Grimble is in the concussion protocol. McDonald could be limited early in the week as the Steelers (7-3-1) prepare for a visit from the Los Angeles Chargers (8-3).
Grimble, the third-string tight end after McDonald and Jesse James, had a critical fumble at the goal line in a loss at Denver on Sunday. Tomlin added linebacker Bud Dupree has a pectoral injury that could make his status uncertain.
Pittsburgh right tackle Marcus Gilbert could practice this week after missing the past five games with an ankle injury. Defensive end Stephon Tuitt could also return after missing two weeks because of an elbow injury.