The Germany midfielder joined the Red Devils from Bayern Munich last summer and had been a regular fixture in the United first team before he picked up a knee injury back in January.
Van Gaal has revealed that he had to convince the United hierarchy that signing the veteran midfielder aged 31 would be a good move for the club.
And the Dutchman is confident that the World Cup winner will soon rediscover his best form once he makes his return from injury.
Van Gaal told United’s website: “Manchester United has bought him even though he is now 31, so I had to convince the board to buy him, because he’s a very good player and he always gives a team more balance,” the boss continued.
“He played very well at Wolfsburg and then began to reach the level he showed at Munich – I think he can [get back to it].”
Van Gaal watched his side slump to a disappointing 2-1 defeat by Sunderland at the Stadium of Light on Saturday as they were dealt a fresh blow in the race for a top-four finish.
The Red Devils are currently fifth in the table and six points behind fourth-placed Manchester City.
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