Bayern Munich star Arjen Robben has urged coach Jupp Heynckes not to rotate his team too much.
Bayern have won all six of their matches so far but have not fielded the same starting XI in any of them, and Netherlands international Robben has voiced concerns about the chopping and changing.
He told kicker: "It is important to maintain your rhythm, and consistency within the team is important."
Robben sat out the Bundesliga matches against Stuttgart and Mainz through injury, but played against Valencia in the Champions League on Wednesday.
His comments brought a swift response from Heynckes, who said: "I won't explain to my players why I make changes. They just have to accept it.
"It would be careless to not rotate players. Including the national games, we've got 24, 25 matches coming up before Christmas. I need to make changes so we still have energy in the spring."
The Bayern coach benched in-form Mario Mandzukic and Thomas Muller for the Valencia game, and also left Luiz Gustavo out. Gustavo told Bild: "The coach does not have to explain it. I am just a player. I am not angry with him."
Former Schalke 'keeper Manuel Neuer, who will be playing, is returning to his old club for a second time.
He was given a hostile reception last season, and Schalke director of football Horst Heldt said: "It's not Schalke vs Neuer, but Schalke vs Bayern. We need the fans to put their focus on our team only.
"That was not the case last year. We won't accept anything beyond the boundaries of good taste."
Schalke director Clemens Tonnies added: "My wish for that match is a Schalke win - and that Manu is not as good as usual."