Sunderland defender Paul McShane faces a race to be fit for the start of the new season after suffering a knee injury while on holiday.
The 22-year-old Republic of Ireland international has already undergone surgery on a fractured kneecap, but may not recover in time to challenge for a place in Roy Keane's first starting line-up of the new campaign.
Sunderland's head of medical services, Dr Glenn Rae, told the club's official website: "It was a very complex fracture, but we managed to get Paul back with us straight away so he could get the best possible attention.
"The operation was a success and Paul will now undergo intensive rehabilitation during the course of the pre-season.
"We're hopeful he'll be able to return to action by the start of the new season."
Meanwhile, Keane has been linked with a move for veteran midfielder George Boateng, if the Dutchman decides to leave the Teessiders this summer.