Arsenal boss Arsene Wenger admitted his side were not at their best during Saturday's 2-1 derby win over Tottenham.
Goals from Emmanuel Adebayor and Nicklas Bendtner either side of a strike from Dimitar Berbatov were enough for all the points at the Emirates Stadium.
However, goalkeeper Manuel Almunia saved Robbie Keane's second-half penalty to ensure the Gunners remained top of the Premier League table at Christmas.
"It was a very difficult victory and we were not at our best," admitted Wenger.
"What was important for us was three points against a side that has improved tremendously in recent weeks.
"We prefer to be where we are in the table and will have a happy Christmas.
"We weren't sharp in the first half and we needed to raise our game.
"When we went ahead we looked like we were in control but we let them back into it.
"Overall, we are conscious that we were not at our best, only in patches.
"They missed a sitter and Almunia's penalty save was the turning point in the game."
Meanwhile, Wenger reiterated his confidence in Almunia, who has replaced the unhappy Jens Lehmann as his number one this season.
"I am not in the situation where I have any bad feelings towards Jens Lehmann," he added.
"He is a 200 per cent professional fighter but we have three goalkeepers of top class and the two who do not play can feel that my decisions are not justified - (Lucasz) Fabianski can feel that as well.
"At the moment Almunia is doing very well."