Chelsea manager Carlo Ancelotti admitted his side had not played well after seeing their 100 per cent start to the season disappear at Wigan Athletic.
The Latics took full advantage of a red card shown to goalkeeper Petr Cech after goals from Titus Bramble, Hugo Rodallega - via a penalty - and Paul Scharner wrapped up a 3-1 victory at the DW Stadium.
The Blues saw Manchester United leapfrog them at the top of the table and afterwards Ancelotti offered no excuses.
"We did not play a good game - it was a bad performance," admitted the Italian.
"I do not know why we did not play well. But these things can happen after a lot of victories. We have to accept this loss and fix things for our next match.
"Wigan played better than us. They were well organised and played good football. I was surprised. This was the right result.
"We played well in the first ten minutes but when we lost the first goal it became more complicated.
"We started the second half better, then there was the penalty. I do not want to comment on it. I know Cech was unhappy but that is normal in that situation."
Ancelotti also refused to criticise his side for conceding a late third goal after Ashley Cole has limped off with an ankle injury and they had already made all three substitutions.
He added: "It was impossible at the end of the match with nine against 11 when Ashley was injured.
"We are disappointed at what happened in this game. I did not rate this performance but in football you have to look forward.
"We might not be top of the table now but there will be a lot of competition and change until the end of the season."