He said: "At the moment, Chelsea have been discreet but efficient. Avram is a completely different profile as he is not very noisy. Every manager has his own personality . . . his team is efficient and I believe his results speak for themselves.
"I am not surprised how well they have done. Before Mourinho arrived, Chelsea were second in the league and were in the semi-finals of the Champions League.
"They already had good results and Mourinho brought them up to win the title.
"Credit to Grant. But you should not expect a 52-year-old who has coached all his life to come in and see the team collapse. He has done well and credit to him for getting a new four-year contract."
Chelsea hitman Didier Drogba will miss the game through injury but Wenger will still warn his defence about the Blues' firepower. He added: "I rate Drogba. He always gives us a hard time and he is a fighter. But when you can replace him with Shevchenko you should not be miserable."