Blackburn's medical staff will assess the injury Aaron Mokoena today to discover the extent of the problem.
The South African had to be stretchered off the pitch after going down under his own weight during Wednesday night's 2-1 win over Portsmouth.
Initial reports suggested it may be a broken leg but Rovers boss Mark Hughes was hopeful the injury was not as serious as first feared.
"There was a lot of concern for Aaron," said Hughes. "He went off after treatment and obviously felt well enough to come back on but then collapsed under weight of his own leg.
"You obviously don't like to see that, and we can only hope that it doesn't prove to be as serious as it looked initially."