Mamadou Sahko may have played his last game for Crystal Palace after being stretchered off with a knee injury during Wednesday's 1-0 defeat at home to Tottenham Hotspur.
Sakho, who has been in fine form since joining on loan from Liverpool in January, was hurt as he pursued Harry Kane in the 56th minute, his left knee twisting after he caught his studs in the turf.
He was carried off on a stretcher, with Damien Delaney replacing him.
"He has hyperextended the knee," Palace manager Sam Allardyce told Sky Sports at Selhurst Park.
"It is certainly serious enough to keep him out for who knows how long. We won't know until we diagnose it.
"But if it is ligament (damage), it may be the end (of his loan spell), it may not."
Sakho, 27, joined Palace after falling out of favour with Liverpool manager Jurgen Klopp at Anfield.
The hulking French centre-back has played a pivotal role in a run of six wins in nine games that has steered Palace clear of the Premier League relegation zone.