Louis van Gaal has admitted Manchester United need to bolster their defence, after being forced to use Darren Fletcher as a centre-back during the second part of their 7-0 victory over LA Galaxy.

During a recent press conference, the United boss had claimed that he wanted to assesses his current squad during the pre-season before making new signings.

"I want to learn about my players, to know them and when I give the orders, I want to see how they perform. I want to give all the players a chance to show themselves under my guidance," he said.

However it looks as though the Dutch boss has already identified that United need a couple of centre-backs, as the departures of Nemanja Vidic and Rio Ferdinand have left a huge gap in the squad.

"I have no more defenders. So I have to pick a player [Fletcher] who can do the job but he is not so suitable for this position," van Gaal told Manchester United's official website.

Van Gaal adopted a 3-5-2 formation against LA Galaxy, similar to the one he used with the Netherlands at the World Cup, with Jonny Evans, Chris Smalling and Phil Jones forging the starting back-line.

Nevertheless, the Dutch boss was forced to entrust the defence to midfielder Fletcher and youngsters Tyler Blackett and Michael Keane in the second half, due to the lack of players able to fill in that role.

Having already spent £56m on Luke Shaw and Ander Herrera, Van gaal's latest quotes suggest his next big investment will be in the defence - even though he is also reportedly chasing a top star such as Arturo Vidal or Angel Di Maria.

Borussia Dortmund star Mats Hummels was said to be his top priority for the back line, but with the Germans unlikely to negotiate his departure recent reports claimed that van Gaal is considering other alternatives including Arsenal's unsettled Belgian Thomas Vermaelen, as well as Dutch duo Daley Blind and Stefan De Vrij.