Bayer Leverkusen said on Sunday that midfielder Michael Ballack has had another injury setback.
The 34-year-old midfielder was unable to train due to a problem with his knee and underwent an MRI scan at the team doctor's clinic in Cologne on Sunday morning.
Results of the scan are not yet known.
He was an unused substitute in Leverkusen's 3-0 win at Eintracht Frankfurt on Saturday.
Ballack, capped 98 times for Germany, returned to action in January after four months out with a shinbone injury sustained against Hannover in September.
The former Chelsea player also missed the World Cup with an ankle injury.