Borussia Dortmund goalkeeper Roman Weidenfeller is a doubt for Saturday's top-of-the-table clash with Bayern Munich after twisting his knee in training.
Weidenfeller limped away from training in pain on Tuesday after a clash with Mats Hummels and tests should reveal the extent of the injury.
"I hope it is just twisted, but it really hurt and the knee has swollen up a lot,'' said Weidenfeller to Bild. "I have a lot of pain.''
Weidenfeller has conceded just 13 goals in 23 games this season and has been an integral part in Dortmund's march towards the Bundesliga title.
Should he be unable to play, back-up goalkeeper Mitchell Langerak will make his debut for the club against Bayern.
Meanwhile, Dortmund have extended the contract of full-back Marcel Schmelzer until 2014.
The 23-year-old, who started his professional career with the Westphalian club in 2005, has played every single game for Jurgen Klopp's side this season and made his debut for the German national team in their friendly international with Sweden last November.
"I am really delighted to have reached an agreement with Dortmund since I never had any doubt that Borussia Dortmund was the place for me,'' he said on the club's website.
Dortmund's director of sport Michael Zorc added: "With Marcel Schmelzer, we have tied down to Dortmund, long term, another important player for the future planning of our team.''
Last October, Dortmund extended the contract of Mario Gotze until 2014 while Mats Hummels is expected to extend his current deal beyond 2013 in the near future.