Steelers running back James Conner had his arm in a sling after leaving the team's 27-14 win over the Dolphins on Monday late in the fourth quarter.
Conner, who rushed for 145 yards and a touchdown, appeared to land awkwardly on his shoulder on a tackle just before the two-minute warning.
Coach Mike Tomlin told reporters afterward that Conner was being evaluated for an injury to the AC joint in his shoulder.
The injury comes at a bad time for the Steelers with backup Jaylen Samuels still recovering from knee surgery earlier this month. And third-string back Benny Snell left the game with a knee injury.
The rash of injuries has led to speculation Pittsburgh will be looking for a back before the trade deadline Tuesday.
Given that the injury happened with the Steelers holding a comfortable lead, Tomlin will undoubtedly come under fire for having his star running the ball in garbage time.