Chelsea boss Carlo Ancelotti admitted his side have to defend better at set-plays after they crashed to a second successive away defeat.
Aston Villa defenders Richard Dunne and James Collins both scored with headers following corners by winger Ashley Young, after Didier Drogba had given the Blues an early lead.
Ancelotti's side had also conceded a similar first goal when losing 3-1 at Wigan and he is aware they have to rectify the problem sooner rather than later.
The Italian said: "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.
"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."