Manchester United captain Nemanja Vidic has been ruled out for two months after undergoing a knee operation.
Vidic, 30, sustained an injury to the same knee in December 2011 that ruled him out the remainder of that campaign but returned to action for the club's Premier League opener against Everton this season.
He has made five appearance since his comeback but was left out of the 2-1 victory over Liverpool this weekend after complaining about the problem, with Sir Alex Ferguson saying at the time: "He felt a bit tight around his knee and we decided to give him a break."
He has now had surgery to rectify the issue and is likely to return in late November.
A club statement read: "Nemanja Vidic has had a meniscus operation on his right knee and will be out for around eight weeks.
"Sir Alex, as a precautionary measure, rested Vidic at the weekend, after he complained of tightness in his knee; however, further medical investigation revealed the underlying problem. The central defender was operated on this week and will be sidelined for about eight weeks."
United are already without Phil Jones and Chris Smalling, who have both yet to feature this season, and Rio Ferdinand and Jonny Evans are currently the only senior centre-backs available.
Michel Carrick has deputised in the position on several occasions, including the first two Premier League games of this season, while 20-year-old Scott Wootton, who spent time on loan with Nottingham Forest last season, could come in to make his first-team debut for United.