Louis Saha is set to be sidelined for two weeks with a groin injury.
Saha has scored 12 goals this term
The Manchester United striker, 28, lasted just 30 minutes of the 2-2 draw at Newcastle before being forced off.
Manager Sir Alex Ferguson confirmed: "It's a groin injury, so it could be a couple of weeks. But who knows? We will assess it properly on Tuesday."
The Frenchman's injury heightens the chances of new loan signing Henrik Larsson making his debut in the FA Cup third round match against Aston Villa.
The Swede, who joined from Helsingborg on a three-month deal, could come up against his former Celtic manager Martin O'Neill.
606 DEBATE: Your reaction to Saha's injury
If the 35-year-old fails to get a game against his old Bhoys boss in the cup, he will get a second bite of the cherry when the teams meet in the league the following weekend.
Ferguson can also call on the services of Ole Gunnar Solskjaer, 33, who is back to full fitness and scored two goals in the festive programme.
If Saha's initial prognosis of a fortnight on the sidelines proves correct he will be back in contention for United's Premiership match against Arsenal on 21 January.