Berlin - Bayern Munich's bad luck continued on Wednesday as new signing Serdar Tasci suffered concussion in his very first training session and had to sit out his introductory press conference.
"He went into a collision with his head and was shaken, it means he has a slight concussion. It's a bit unfortunate," admitted Bayern's director of sport Matthias Sammer.
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The Bundesliga leaders expect the defender to be out for the next two or three days and it is unclear whether he will be fit for the runaway Bundesliga leaders' next league match at fourth-placed Bayer Leverkusen on Saturday.
Germany international Tasci, 28, only signed on a six month loan deal from Spartak Moscow on Monday as emergency cover after the Bavarian giants were plagued by a run of injuries in defence.
With Javi Martinez, Jerome Boateng and Medhi Benatia all out, Bayern coach Pep Guardiola has just one fully-fit centre-back in Holger Badstuber.
Martinez underwent knee surgery in Barcelona on Tuesday, and the club has said the Spanish international will be out for four weeks, while Boateng is expected to be out for three months.
Tasci has been at Spartak since 2013, starting 16 of their 18 leagues fixtures so far this season, and Bayern paid 2.5 million euros ($2.8 million) fee for his loan.