Chelsea boss Carlo Ancelotti admitted his side have to defend better at set-plays after they crashed to a second successive away defeat to Aston Villa.
Defenders Richard Dunne and James Collins both scored with headers for Villa following corners by winger Ashley Young, after Didier Drogba had given the Blues an early lead.
"We are disappointed because I think we played a good match but we lost this game on the set-plays and I don't like to lose the game on the set-plays," said Ancelotti.
"It is better we lose when the other team play better than us. Villa did a very good job but Chelsea also produced some very good play.
"On the set-plays we need to do better. We can do better. We have to put more pressure on and have more markers in the box.
"With Wigan, we did the same mistakes. The first goal was a set-play and we have to work to improve this situation.
"We have to pay more attention to those situations in the box. We work every time on the set-plays but we have to maintain more focus on this situation."
Ancelotti added: "When we lose a game, for sure we are not happy but I think until this moment, the team has played very well, done a very good job.
"But we can improve, for sure, and, again I say, set-plays is one of those things we have to improve. In England there are a lot of players who are very good with their head."