The Dutch winger Robben is said to have grabbed World Cup top scorer Mueller by the throat after the final whistle, allegedly disgusted that Mueller made a disparaging gesture after he executed a late free-kick poorly which he did not want Mueller to take.
'I really hate it when the players throw up their arms in such a way on the pitch. That is not respectful and we shouldn't be doing that,' said Robben.
Anatoly Tymoshchuk separated the two players. Mueller did not comment while Lahm said the issue would only be discussed internally.
Van Gaal said he didn't see what exactly Robben did but said that player should discuss issues.
'It is common in the Netherlands that we argue and speak out what is on our mind. There is a different culture in Germany,' van Gaal said.
The issue made more headlines on Sunday in the German media than the 3-1 victory with which Munich climbed into third place in the league. Robben only returned to action a fortnight ago from a hamstring injury which had sidelined him since July. (AFP)