Sunderland forward Duncan Watmore has suffered a suspected cruciate knee ligament injury just six games after returning to action following 10 months out with a torn ligament in the same knee.
Watmore limped out of Sunderland's 2-2 draw with Millwall on Saturday and fears are that his injury is again serious.
The 23-year-old is set to undergo surgery later this week once scans have determined the full extent of the damage.
Chris Coleman, who was unveiled as the club's new manager on Monday, admitted Watmore's injury was a major concern.