Bayern Munich coach Jupp Heynckes has warned Arjen Robben could be out for a month after undergoing surgery on an inguinal hernia after suffering with a groin problem all season.
The Dutchman will subsequently miss Saturday's clash with Hertha Berlin having been told to rest for fortnight, but the manager fears it could be longer.
Heynckes told the club's official website: "The fact is Arjen needs to rest for 14 days and then he will start with light training.
"We cannot say precisely when his comeback will be.
"I believe it will be several weeks before he is available again."
The Dutch star has scored twice for the German Bundesliga leaders so far this season in four appearances.