Thomas Muller has been told by Bayern Munich chief Karl-Heinz Rummenigge he needs to ask if he wants to leave for Manchester United this summer. According to reports in German newspaper Bild, the forward would be open to joining Louis van Gaal's revolution at Old Trafford this summer in a move worth £37million. Van Gaal was the manager who installed Muller as a first-team regular at Bayern during the 2009-2010 season and the prospect of a reunion would tempt the Germany forward. But first he needs to persuade the club's chief executive Karl-Heinz Rummenigge to sell him. Rummenigge told Bild: 'If a player does not feel comfortable with Bayern Munich, he must come to my office. Then you have to talk about it.' Muller, 24, has started 24 Bundesliga and eight Champions League matches this season but has only completed the full 90 minutes in 18 of these and reportedly considers this insufficient for a World Cup year.