The home side scored twice inside the opening 10 minutes at Stamford Bridge before the Gunners were reduced to 10 men.
"We had momentum but it stopped last Saturday against Aston Villa for some reason. Now we are trying to build more momentum," BBC Sport quotes the manager as saying.
"The victory over Galatasaray was important. This was the most important match of the season for Arsenal. For us it was an important game.
"At 2-0 after seven minutes the game is over. We were too strong. Then came the penalty and red card but the game was resolved in 10 minutes."
The result left Chelsea seven points clear at the top of the table ahead of this afternoon's kickoffs.