Chelsea boss Andre Villas-Boas felt his side 'paid a high price' for failing to make the most of their chances as they were handed a 3-1 home defeat by Aston Villa.
Stiliyan Petrov and substitute Darren Bent both scored in the final seven minutes of the game to put another nail in the Blues' Premier League title bid.
Didier Drogba's penalty - his 150th Chelsea goal - had given the home side the lead but Stephen Ireland restored parity before the late drama at Stamford Bridge.
And Villas-Boas told Sky Sports: "It was similar to the last home game against Fulham to some extent. We dominated the second half with possession and created enough chances to win the game.
"They didn't manage to convert them and we ended up paying a high price for a couple of mistakes on the counter-attack.
"Aston Villa were always very threatening thanks to good work by their manager Alex McLeish in transition, so they got a very deserved win and respectful win.
"We tried hard and we had good chances to go one goal up, but in football if you don't take your chances, then it makes life a little bit hard and that's exactly what happened."
Asked what the Portuguese boss can do to restore some confidence in his side going into 2012, he added: "I think the belief was in our side and we pushed Villa at the back and managed to create big goalscoring opportunities.
"What Villa did was extremely effective and they exploited us on the counter-attack.
"I don't think that has anything to do with confidence or anything else. We are working hard and we try to see if 2012 will bring us better news."
Villas-Boas vented his anger at the fact that his side were having to play two games inside 48 hours with the clash at Wolves coming up on Monday, adding: "I think it's difficult to play again within 48 hours. I mean, I respect the festive period in England but I don't think there is a lot of common sense by putting players at risk and playing 48 hours after. It's a tremendous risk and it can lead to serious injuries of maybe the English national team players and for me it makes no sense.
"Even so, if all teams must go through this period, we must assume the challenge that we have ahead and must recover players but we respect the festive period."