"Bastian got a knock on the calf. At the moment it does not look good," Heynckes told reporters. "This is normally a difficult injury. We now have to wait and see if it affects the muscle or not. Then we will be able to say more."
Schweinsteiger scored Bayern's second goal with an 18-metre drive.
The Bavarians, who opened up a four-point lead in the Bundesliga with their win, also top their Champions League group on seven points from three games, two ahead of Napoli.
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