Borussia Dortmund may be without first-choice goalkeeper Roman Weidenfeller for Saturday's trip to the defending champions, Bayern Munich.
Weidenfeller was forced out of a training session on Tuesday after a collision with defender Mats Hummels and is believed to have suffered a knee injury.
If the 30 year old fails to recover before the Bayern match, Australian youngster Mitchell Langerak could make his first-team debut in the Bundesliga showdown at the Allianz Arena.
"I could hear a noisy crack around the knee," Weidenfeller was quoted as saying by newspaper Der Western.
Weidenfeller will undergo an examination by team doctor Markus Braun.
Some sources have suggested Dortmund's captain has only suffered a minor strain and will be fit to take his place in Saturday's showdown with the defending champions at the Allianz Arena.
But other reports claim the joint is still swollen, indicating the possibility of a torn or damaged ligament.
If Weidenfeller has suffered any significant damage, 22 year old Langerak could find himself directly in the firing line as Dortmund—10 points clear at the top of the table—go in search of their first league title since 2002.
Langerak signed his first professional contract with A-League club Melbourne Victory in 2007 after a year at the Australian Institute of Sport.
He took over from New Zealand international Glen Moss on a regular basis in the 2009/10 season before earning a move to Dortmund.
Victory initially rejected an approach from the German giants, before eventually agreeing a reported fee of close to AUD$1 million.
He is mid-way through the first season of a four-year deal at the Westfalenstadion.