Burnley have confirmed Martin Paterson will be out for up to three months after undergoing a knee operation.
Paterson twisted his knee in the early stages of Burnley's defeat by Barnsley in the Carling Cup on Tuesday night and manager Owen Coyle feared the striker would require a lengthy lay-off.
The Northern Ireland international underwent exploratory surgery on Wednesday night, which showed a tear in the cartilage.
The Clarets now expect Paterson to be sidelined until December and his injury compounds Coyle's selection problems.
Earlier this week, Chris McCann was ruled out for three months after the midfielder damaged medial knee ligaments in last weekend's 3-1 win over Sunderland.
Paterson had failed to score in eight appearances for Burnley so far this term, but was the club's leading marksman last season after netting 19 times.
In addition to missing a large chunk of the Clarets' campaign, the 22-year-old will also sit out Northern Ireland's final 2010 World Cup qualifier against Czech Republic next month.