Michael Carrick will miss at least the first month of the new season after undergoing surgery on his ankle.
The England midfielder picked up the injury in training and Manchester United confirmed the news via social media on Thursday.
The club tweeted: "Michael Carrick has had surgery this morning on his left ankle ligaments and will be out for 10-12 weeks."
Michael Carrick has 31 international caps
Carrick's new boss Louis van Gaal - who was introduced to the media on the same day - said that Carrick's injury comes at an unfortunate time.
He said: "It is a big blow because he is a very experienced player."
Manchester United are about to embark on a busy summer of pre-season action, beginning with a tour of the United States.
They face LA Galaxy on 23 July, and also take on Roma, Inter Milan and Real Madrid while in the US - with Carrick now set to sit out the entire trip.
He is also likely to miss Premier League games against Swansea, Sunderland, Burnley, QPR, Leicester and West Ham.
England take on Norway at Wembley on 3 September, before getting their Euro 2016 qualification campaign under way in Switzerland five days later.
Both fixtures are likely to come too soon for Carrick.
