Arsenal manager Arsene Wenger laid into his players for the way they conceded the goal to Chelsea in the 1-0 defeat.
The Gunners went down to a 73rd-minute Didier Drogba goal that struck his knee and bobbled in and Wenger said: "We basically gave away a very stupid goal.
"This game was all about who made the first mistake and we lost as it was us.
"I don't think there is a difference in quality between the teams. I feel my squad needs more belief and not to accept losing games like that."
He added: "We had enough possession to score goals but we just missed something - we need to be more efficient.
"There were lots of positives but we have to acknowledge we gave away a stupid goal and didn't score.
"The goal was a defensive error because you shouldn't allow your opponent to be in a position where he can have luck.
"We had about four good chances and, in a game like that, four chances are enough to score a goal, you won't get 10 or 20.
"But the team can take a lot of belief from today."