Wayne Rooney could be on the bench for Premier League leaders Manchester United against West Ham, but defender Nemanja Vidic is definitely out.
The England striker injured his hip against Chelsea last weekend and missed the Champions League semi-final victory over Barcelona.
But United boss Sir Alex Ferguson said Rooney could be involved at Old Trafford.
Patrice Evra is also available after being carried off on Tuesday after being kicked in the face.
Ferguson said on Friday: "Vidic is not fit for tomorrow as with concussion you are out for 10 days but he should be fit for next Sunday.
"Rooney has given himself a chance but I don't know if he will start, maybe he will be on the bench.
"There has been a lot of improvement in the lad and the bruising on his hip has broken up, but we will still have to see whether he can make tomorrow.
"We have got a cup final of major importance and we want to make sure he is available for that, so we are not rushing him. We need to make sure he is 100%."
West Ham expect winger Julien Faubert to shake off a slight hamstring problem.
Midfielder Freddie Ljungberg (cracked rib) has been added to the long list of injuries.
Defender Anton Ferdinand (hamstring) has returned to light training, but is not expected to feature at Old Trafford tomorrow - and neither is fellow centre-half Matthew Upson (calf).
Squads:
Manchester United: Van der Sar, Neville, Brown, Ferdinand, Silvestre, Evra, 0'Shea, Ronaldo, Scholes, Anderson, Nani, Hargreaves, Carrick, Giggs, Park, Fletcher, Rooney, Tevez, Kuszczak, Pique, Welbeck.
West Ham: Green, Pantsil, Tomkins, Neill, McCartney, Faubert, Parker, Noble, Boa Morte, Zamora, Ashton, Walker, Mullins, Cole, Solano, Sears, Spector, Collison.