Porto - Jose Mourinho was left to defend his team selection and his side's performance after their slump continued on Tuesday with a 2-1 Champions League defeat to Porto.
Maicon got what proved to be the winning goal for Porto at the Estadio do Dragao after a superb Willian free-kick had cancelled out Andre Andre's opener in a tremendous Group G encounter as Mourinho returned to face his former club.
The Chelsea manager was furious with his team's display in drawing 2-2 with Newcastle United in the Premier League last weekend and made significant changes to his line-up, but on this occasion he simply said that two mistakes cost them dear in Portugal.
"It was a performance with two ridiculous mistakes. Sometimes you make that kind of mistake and you are not punished but we were," said Mourinho of Chelsea's defending of the corner that produced Maicon's winner and of a later delivery that Danilo headed off the post.
"The second goal is a really bad mistake. We watch dozens of repetitions of Porto taking corners - I thought we were completely ready for that.
"We had another similar mistake when they hit the post but apart from that it was a balanced performance. The defenders played well, had no problems, but two ridiculous mistakes and we were punished."
Mourinho, who coached Porto to Champions League glory in 2004, has now gone back to his old club three times with Chelsea and is still to win.
This defeat followed a loss by the same score in late 2004 and a 1-1 draw in 2007, but of more importance is the defeat in the context of Chelsea's season.
They languish in 15th place in the Premier League and have already suffered five defeats in 11 games in all competitions, winning only four times.
"The players reacted in a positive way," added Mourinho of their second-half performance, when Diego Costa hit the woodwork and Chelsea had appeals for a penalty for handball against Ivan Marcano waved away.
"They tried to get a result. Diego hit the post, (Branislav) Ivanovic had a chance one metre from goal, there was a last-minute situation, a clear penalty.
"So for me, I don't think my players deserve me to be critical at them. I'm not going to point the finger at one or another, but two mistakes cost us the game, a game that I think was fantastic."
He insisted that his team remained in a good position to qualify for the last 16, despite slipping to third in Group G behind Porto and Dynamo Kiev, who won 2-0 at Maccabi Tel-Aviv.