Chelsea head coach Carlo Ancelotti blamed a lack of concentration at set-plays for his side's 2-1 defeat at Aston Villa.
The Blues were knocked off the top of the Premier League table by Manchester United after two goals from corners at Villa Park inflicted a second defeat on the London club in the space of three games.
"I am disappointed because we did a good match, but we lost the game on the set plays and I don't like to lose the game on the set-plays," claimed Ancelotti.
"If you have to lose a game it is better to lose when the other team played better than us. Aston villa did a very good job but also Chelsea did very well.
"On the set-plays for sure we need to do better because we can, we need more pressure and markers in the box. This is the question for this match."
Ancelotti admitted there were parallels to be drawn between Saturday's defeat and the 3-1 loss at Wigan Athletic last month which ended Chelsea's 100 per cent start to the season.
"In Wigan we made the same mistake, the first goal was a set play and we have to improve this situation because it is an important one in the game. We have to pay more attention in the box," added the Italian.
"In England there are a lot of players (that are) very good with their head and it is a dangerous situation.
"When we lose a game we are not happy but until this moment the team have played very well, did a very good job, but some things we can improve for sure, set-plays is one of these things."