Andre Villas-Boas has hit out at former Chelsea midfielder Michael Ballack following recent criticism.

The German claimed that his Bayer Leverkusen side sensed that the Blues were lacking mental strength as they beat them 2-1 in the Champions League on Wednesday.

"Michael is always very self-opinionated," said Villas-Boas. "I disagree with him. He doesn't live in this dressing room. He used to live here before and he didn't solve all the problems before."

Ballack joined Leverkusen in summer 2010 after four years at Stamford Bridge.