Brentford top scorer Bryan Mbeumo will be ruled out for several weeks due to a "bad" ankle injury picked up in the Bees' 2-1 loss to Brighton.
The 24-year-old netted his seventh goal of the season from the penalty spot, before being substituted off injured.
"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 not play on Saturday [against Sheffield United]."
The injury could put the Cameroon forward's preparation for the African Cup of Nations at risk, with the tournament set to begin on 13 January next year.
The Indomitable Lions face Guinea in their opening Group C game on 15 January.
Mbeumo is one of eight first-team players currently ruled out for Brentford, having taken on extra responsibility in attack during Ivan Toney's suspension for breaking football's gambling rules.
"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]", Frank said.
"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."
