Mario Gotze could miss the rest of the season after tearing his left hamstring against Real Madrid on Tuesday.
The injury occurred in the 12th minute of Borussia Dortmund's UEFA Champions League semi-final, which the German side lost 2-0 on the night, progressing 4-3 on aggregate.
The Germany international pulled up straight away and went over to the Dortmund bench clutching the back of his leg.
"Mario picked up a muscle strain. It's going to be a race against time for the fixtures to come," Dortmund manager Jurgen Klopp said.
"It's going to be close for him for all the games we have left."
The 20-year-old will definitely miss the fixture against Bayern Munich on Saturday and remains a doubt for the UEFA Champions League final.
It could be the last time Gotze appears for the club after it was confirmed he would join Bayern in the summer.