Brentford winger Bryan Mbeumo faces several weeks sidelined with an ankle injury.
Mbeumo broke down in defeat to Brighton.
"It is bad. He'll have a scan later, but we don't know the exact number of weeks he will be out," Brentford manager Thomas Frank said.
"He will definitely not play on Saturday [against Sheffield United]."
He added, "His work rate for the team is incredible - you don't see many wingers who work so hard and mean so much [to their team].
"He has become the key man - 'give me the ball, I'll take this'. Who will that man be now? We'll find out in the next weeks."
