Chelsea assistant-manager Steve Clarke felt Michael Essien went some way towards justifying his ?24million transfer fee with his display in the Blues' 2-0 win at Charlton on Saturday.

Goals from Hernan Crespo and Arjen Robben secured victory in the top of the table clash at The Valley, extending the champions' run in the Premiership this season to six wins from six games without conceding a goal.

However, it was the display of Ghana midfielder Essien, who Chelsea pursued for months before finally persuading Lyon to sell, that most impressed Clarke.

"He had an interrupted pre-season, because of the transfer saga, but he is a top quality player," Clarke told the club's official website.

"We knew that and that is why we paid the money for him. Every game he is getting stronger and I'm sure he'll get better and better as the season goes on.

"It's a different culture, different team-mates but he has settled in very, very quickly."

Jose Mourinho's right-hand man also had words of praise for Chelsea's rock-solid back-line.

He added: "We didn't look like conceding. Teams will always put you under pressure in certain moments of the game but we defended very well, as we did last season. It is one of the strengths of our team.

"We've played six games, won them all, conceded no goals and scored 12. It is a very solid start and we are all delighted with it - but there is a long way to go."