The Germany captain picked up the knock in the scoreless draw against Newcastle last week, and was operated on Friday after consulting the German national side's staff doctor.

The DFB said they did not know how long Ballack would be sidelined while he recovers. The statement did not say whether the 30-year-old will play again this season.

Chelsea's chances of defending their Premiership crown took a knock on Saturday when they drew 2-2 with Bolton and leaders Manchester United beat Everton 4-2 to secure a five-point lead.

Jose Mourinho's men play the second leg of their Champions League semifinal against Liverpool with a 1-0 first leg lead this week.