Bayern Munich winger Arjen Robben could miss the start of the season after being ruled out for six weeks with an adductor muscle injury.
The 32-year-old Dutchman missed the last two months of 2015-16 with a similar injury and pulled up in their pre-season opener against fifth-tier Lippstadt.
He only made 15 Bundesliga appearances last season.
Bayern face Borussia Dortmund in the German Super Cup on 14 August.
The German champions' league opener is against Werder Bremen on 26 August.