Steven Fletcher added to Sunderland manager Martin O'Neill's woes after picking up an ankle injury during the Wearsiders' 2-1 defeat to Norwich.
O'Neill's side are hovering precariously above the relegation places after they squandered a host of chances as they were beaten at Carrow Road on Sunday.
Fletcher, who has scored six goals for Sunderland this season, failed to come back on after half-time as he was replaced by Connor Wickham.
"I'm really not sure, at this moment he is sore," O'Neill told Sky Sports. "The doctor is with him as we speak and I really will not know about the injury properly until Monday or Tuesday."
O'Neill was left to rue his side's inability to convert their chances, with Matthew Kilgallon missing an open goal from 10 yards out, but the former Norwich manager is taking positives from defeat.
"We conceded some poor goals and that gave us an uphill task," O'Neill said. "From the moment we conceded the second goal I thought we played really strongly. The second half in particular we were really excellent and we created some decent chances and should have scored two or three.
"If we show the same spirit as we did in the second half for the rest of the season we will be fine."