Rafael will miss Sunday's Carling Cup final and a further month of action, having suffered a fractured ankle.
The 18-year-old, who has been a revelation in his first season at Old Trafford, sustained the injury in last weekend's victory over Blackburn, and Sir Alex Ferguson admits it is a heartbreaking setback for the Brazilian.
"Rafael is out for a month with a slight hairline fracture of his ankle," he told his pre-match press conference. “It’s a blow for the kid because he’s been playing in all the games and he’s done so well. He deserves to be in the final.”
More likely to be involved are Jonny Evans, Gary Neville and Anderson, who are all set to travel to Wembley despite recent injuries. Danny Welbeck and Darron Gibson, meanwhile, are both set to start.
"Gibson and Welbeck will both play and deserve to play," said Sir Alex. “Jonny Evans has hopefully recovered from Tuesday’s match. He was feeling his injury towards the end of the game. Like Rafael he deserves to play in the final.
“Other than that everyone’s fit. Neville’s in the squad, he’s been training well for about a week and will travel with us. Anderson played 45 minutes in the Reserves last night and he’ll travel down with us.”
With Edwin van der Sar likely to be rested over the weekend, Sir Alex admits he must make a difficult choice between Ben Foster and Tomasz Kuszczak in replacing the Dutchman.