Robben was forced out of Bayern's goalless draw with Juventus in the Champions League, only playing for 45 minutes at the Allianz Arena.

Scans proved that the injury-prone Dutchman has an irritation of the plica tissue in the knee joint, which requires a knee operation soon.

"The cartilage and ligaments are OK," said coach Louis van Gaal. "We are fortunate also that we have a break next week for internationals."

French winger Franck Ribery is also doubtful for the weekend's league game with Cologne, so is center-half Daniel van Buyten.