Manchester United's defensive injury crisis worsened on Saturday when Matteo Darmian was taken to hospital after colliding with Shane Long in the 1-0 defeat to Southampton.
Red Devils boss Louis van Gaal confirmed on Friday that Ashley Young required surgery on a groin injury, which was expected to keep him on the sidelines for a lengthy spell.
Young had been doing duty at full-back for much of the season as injury had already claimed Luke Shaw, Antonio Valencia and Marcos Rojo.
However, the loss of Darmian has left Van Gaal without all five of his senior full-backs, after the off-season signing from Torino was forced off on the hour mark at Old Trafford, having injured himself badly in a aerial challenge with Long.
"He was spitting blood on the pitch so he has already gone to the hospital and we have to wait and see what happens," Van Gaal said in his post-match press conference.
"That is the fifth full-back who has been injured. Probably there is something wrong in one rib and also the chest but we have to wait and see.
"It was not a nice view for the players to see that. Darmian is bad because he is now in hospital."
The Dutchman felt that United lost their impetus when Darmian came off, with the Saints snatching a late winner through new signing Charlie Austin in the 87th minute.
"At half-time I changed [Marouane] Fellaini and then I saw the first 15 minutes were better and the fans were behind the team and cheering," Van Gaal added.
"But then it was gone after the injury to Darmian. It's a pity that we don't continue with our momentum. But we have to stick together in this period because we have a lot of injuries."