Bayern Munich are uncertain whether Serdar Tasci will be fit to face Bayer Leverkusen at the weekend. Adam Pretty/Bongarts/Getty Images

Serdar Tasci sustained a head injury in his first Bayern Munich training session and appears to have suffered minor concussion, sporting executive Matthias Sammer has said.

Bayern signed Tasci on loan from Spartak Moscow on deadline day to cover for what club president Karl Hopfner has described as a "bad patch" with injuries, with the centre-back set to provide cover during the absences of Jerome Boateng, Javi Martinez and Medhi Benatia.

The club invited reporters to greet the new signing in Munich on Wednesday, but the former Germany international was unable to attend after an incident at his first session with his new teammates.

"He had a collision and in the aftermath showed symptoms," Sammer said. "It indicates he suffers from a minor concussion."