Michael Ballack knows Chelsea will have to spring a few surprises to unsettle former manager Jose Mourinho in their Champions League clash.

Chelsea travel to face their former manager's Inter Milan team at the San Siro on Wednesday having been drawn against what Ballack insists was the worst possible opponent in the Champions League.

Mourinho knows the Blues all too well having constructed much of their squad himself. "He still knows us all very well and that gives this game a special explosiveness," said the midfielder.

"We have unfortunately, as group winners, been given the toughest draw possible.

"But that doesn't bother us - we are looking forward to it, also because the former manager Jose Mourinho is coming."

Although it is already more than two and a half years since Mourinho left the Premier League club, his legacy lives on in the squad which has largely remained intact.

Ballack himself was one of Mourinho's signings when he arrived on a free transfer from Bayern Munich and he expects his former manager to be all clued up about his opponents next week.

"There won't be any information that Mourinho doesn't know about," said Ballack in an interview with Germany's Sat.1 television.

"He always knew everything about every opponent, every player and every tactic.

"He knows the players from his time here and only a few new ones have arrived, but the core of the team has remained the same. He gave us our style of play which has not changed over the last few years."