Chelsea had greater belief and the luck came from the shin of Didier Drogba's shin.
His 73 minute goal gives the champions confidence that they can retain the title they won easily last season.
Both manager's had something to say.
Jose Mourinho was the happier of the two managers.
The Portuguese man said: “This result does not decide who will win the title, nor decide if Arsenal will fail to win the title, it’s just three points for us and none to Arsenal.
But they are now three points behind us.
The game was not a massive one for us. They played reasonably well and I would love for them to give up now, but I know they will not panic.
“Didier Drogba is already a very confident man.
The goals he scored against Arsenal in the community Shield gave him that. He did score a lucky goal today, but that’s how it goes.
“We played okay today. We have six points from two games. Last week was a poor display,
I told my players at halftime to maintain their tactical organisation and show more aggression.
Michael Essien gave us some of that. He made our midfield more secure, but we defended well as a team.
When we scored, I knew we would win, provided their was no individual mistakes.
I saw two equal teams but we had better chances.
Arsenal Wenger said: “I was disappointed to lose to a set piece, we lacked some self belief. We gave the game away, but normally score goals.
“Hleb did well but I don’t want to lose many more games like that.
This is not a transitional period for us. I believe we have a lot of potential.
We can still have a great season. I hope this defeat will prove to be the starting point for it.