Borussia Dortmund full-back Lukasz Piszczek is a doubt for the Champions League semi-final second leg against Real Madrid on Tuesday.
The Poland international featured from the start in BVB's 4-1 win at Signal Iduna Park in the first leg, but was taken off after 83 minutes due to a groin strain.
The length of the 27-year-old's layoff is still unknown, although he will miss Saturday's clash with Fortuna Dusseldorf and coach Jurgen Klopp has conceded he is facing a fitness battle ahead of the trip to Spain next week.
"It's even a race against time for Tuesday," Klopp was quoted as saying on the official Dortmund website.
Tuesday's return at Santiago Bernabeu is scheduled to kick off at 20:45CET.