Eighth-placed Bayern are desperate for points and could close in on the top spots with a win on the first Bundesliga weekend since the suicide of Hanover 96 and Germany keeper Robert Enke.
Dutchman van Gaal has so far had an unspectacular first season in charge and Bayern Munich manager Uli Hoeness said he could not say whether he would still be there after the end of the season.
"The board and Van Gaal deal with things in a critical and honest manner. I cannot keep saying things are great when we are in eighth place," said Hoeness in a joint interview with club president Franz Beckenbauer in Bild newspaper.
"This is hard to say. At the moment there is a certain difficulty between coach and player. We now have five league matches and two Champions League games (until the winter break). We will have to wait for those games," he said.
"I have friends there and it will be a joyous occasion to return. I am not, however, going to Munich to embrace people but to win the match," said Heynckes.
Schalke 04 host Hanover 96 on Saturday in what is expected to be an emotional affair with Enke's death still fresh in the minds of his teammates.
