Michael Carrick
Michael Carrick could miss as many as seven games if he misses the next four weeks of the seasonGetty Images

Manchester United midfielder Michael Carrick could miss the next seven matches after being ruled out for four weeks with a muscle rupture.

The injury represents the 59th separate injury to befall United manager Louis van Gaal in his first season at Old Trafford and it is the second time Carrick has been ruled out for a significant period after suffering an ankle injury last summer.

Meanwhile, Van Gaal has also confirmed fellow midfielder Darren Fletcher will join West Ham United on a permanent basis in the remaining days of the January transfer window.

Fletcher has made just four Premier League starts for United this season and looks set to become the Hammers' second signing of the mid-season window.

"He is at West Ham now I believe, so we will have to wait and see," he said. "He is my third captain so he is an important guy in the dressing room, I like him as a person so we shall miss him. But he hasn't played so many times.

"We have talked about that. He prefers to play. Therefore we have helped him to go away."

Victor Valdes is expected to be United's only addition during the January window, with executive vice-chairman Ed Woodward confirming the club's business would be delayed until the summer.

And Van Gaal has reaffirmed that promise while criticising the timing of the window, which he claims disadvantages smaller clubs.

"I don't think it's favourable for the league because it's a little bit unfair," the United boss said. "You start a league and then you change your team – the richer clubs can do that and it's not fair for others.

"But that's the rule and you can take benefit of it. I read every day that I or United are interested in other players. We only have under contract now Victor Valdes. We gave him a chance. We are only selling players, not buying them."