Germany midfielder Michael Ballack has joined Bayer Leverkusen on a two-year contract following his release by Chelsea.[LNB] The 33-year-old, who is missing the World Cup through an injury picked up in the FA Cup final victory, was released by Chelsea at the end of last season.[LNB]The midfielder is returning to the Bundesliga and his old side, with whom he reached the Champions League final in 2002[LNB]"With my transfer to Bayer Leverkusen a circle is complete. I had a beautiful and successful time here, on which I like to look back on a lot," Ballack said on his new club's official website.[LNB]"That was a factor in my decision."[LNB]Ballack added: "But above all the good sporting potential of this young and attractive team were persuasive.[LNB]"I am especially looking forward to the great fans, who naturally have been key in my decision to return to Bayer."[LNB]Ballack, who spent three years with Bayer before leaving for Bayern Munich in 2002 and then moving on to Chelsea in 2006, will reportedly earn around 12million euros over a two-year stay at Bayer.[LNB]Steve McClaren's Wolfsburg were also believed to have been interested in him, but Ballack has opted for a return to his old club.[LNB]Bayer sporting director is delighted to have signed a player of Ballack's experience, and believes he will help the development of the club's crop of young players.[LNB]"With Michael Ballack our team is getting an enormous boost in quality," he said. "Especially our many young players will benefit from his abilities and his experience.[LNB]"We did everything to convince Michael. That his preference was for Bayer despite our limited financial possibilities in comparison to the competition, shows his emotional attachment to the club."