Pep Guardiola expects Jerome Boateng to return to training in the next 24 hours, but says he cannot guarantee he will be fit for the Champions League semi-finals.
The centre-back has been out of action since January after suffering adductor damage in the 2-1 Bundesliga win over Hamburg.
Boateng said last month that he hoped to be back in action by mid-April, thereby giving him plenty of time to build up fitness before the first leg with Atletico Madrid on April 27.
Guardiola, however, could not offer any assurances over the Germany international's return, telling a news conference on Monday: "Jerome can maybe train with the team today or tomorrow.
"He was injured for three months, so whether he'll be fit for the Champions League semi-final, I don't know."
Bayern face Werder Bremen in the DFB-Pokal semi-final on Tuesday, looking to reach a fourth final in five years and keep their hopes of the treble alive.
Borussia Dortmund could lie in wait should they defeat Hertha Berlin on Wednesday, but Guardiola has warned of the danger of looking too far ahead.
"I want to reach the final. Both Bremen and Berlin also deserve to get there. What would the coach of Berlin think if I wanted a final against Thomas Tuchel? I just want to get there," he said.
"A semi-final is always difficult. They have players like [Zlatko] Junuzovic, or [Claudio] Pizarro. It would be a big mistake to think we are already in Berlin. We have to win first.
"We had problems in the first half against Schalke [on Saturday], but if we play as we did in the second, then we have a good chance of reaching the final.
"I've always rotated in my career. I like rotation. But I'm not thinking about the game with Atletico Madrid or Berlin. Bremen is the only thing in my head."
Arturo Vidal scored one and set up another in the 3-0 victory over Schalke which maintained Bayern's seven-point advantage at the top of the table, and Guardiola admits he has been delighted with his recent form.
"Arturo has played very, very well lately," he said of the Chile international, who scored in both legs of the Champions League quarter-final against Benfica.
"He is really important for the team. He has a great personality, a great mentality. This is a very good quality of his."