(CNN) -- Germany captain Michael Ballack has suffered a fractured left knee cap following a heavy challenge while playing for Bayer Leverkusen against Hanover on Saturday.
The 33-year-old former Chelsea and Bayern Munich midfielder limped off after 30 minutes of the Bundesliga clash and is expected to be out of action for up to two months.
The injury means Ballack has already been ruled out of the Euro 2012 qualifiers against Turkey and Kazakhstan.
It is a further blow to Ballack, who missed the World Cup finals with an ankle injury and was subsequently left out of the Germany squad for this month's ties against Belgium and Azerbaijan.
Germany national coach Joachim Loew released a statement saying: "I feel sorry for Michael that he must accept a new health setback. Of course I wish him a quick and speedy recovery."
Meanwhile, Mainz joined Hoffenheim at the top of the Bundesliga table with a 2-1 home victory over Kaiserslautern on Sunday.
The visitors went into the interval with the lead courtesy of a well-taken goal from Croatian striker Srdjan Lakic.
But Niko Bungert levelled after 71 minutes and Mainz collected all three points with a deflected strike from teenager Andre Schuerrle.
The result means Mainz have won all their three opening matches and they stand on nine points, trailing Hoffenheim at the top only on goal difference.