Left-back Ashley Cole completed the rout in the second half and Blues boss Avram Grant said: "In the last five or six months, the players have given more than 90% good performances and that has made me happy.
"We played very well and used our chances in the first half. In the second half, we played with one man short but very cleverly.
"We controlled the game in the second half and they didn't create one chance really. We needed to play a little bit differently tactically and I think we did it very well.
"I think we have always been in the title race and we need to keep there. I thought the goal we scored in the first two minutes was a good one but we are used to these decisions."