The 40-year-old was substituted in the 60th minute of Bayern's 5-1 Bundesliga win over FC Koln on Saturday after feeling discomfort in his left calf.
Despite finishing the matchday celebrations with his team, further medical checks on Sunday confirmed muscular issues that will require careful management.
Bayern's medical staff have since advised that Neuer "will have to take it easy for the time being", leaving his availability in serious doubt for the upcoming cup final against VfB Stuttgart in the DFB-Pokal on 23 May at the Allianz Arena.
The timing is a major concern for Bayern, with the final just days away. Neuer's leadership and experience remain central to the squad, particularly in high-pressure matches of this magnitude.
Away from club duty, Neuer had already retired from international football, but he was still named in a provisional 55-man squad by Germany coach Julian Nagelsmann for the 2026 World Cup. That inclusion had already sparked speculation about a possible return to the international stage, though this latest injury raises fresh doubts.
For now, Bayern will closely monitor their captain's recovery as they hope for positive signs ahead of a decisive week in their season.
