Chelsea manager Jose Mourinho blamed "two ridiculous moments" after his side's Champions League loss to Porto.
The Blues suffered their fifth defeat of the season in all competitions after Maicon's second-half header gave the home side a 2-1 victory.
"We watch dozens and dozens of repetitions of Porto taking corners. We were completely ready for that," said Mourinho.
The Blues have now lost more games this season than the whole of 2014-15.
They endured just four losses in the last campaign, but have been beaten five times in 11 games this term.
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'Good performance, bad defensively'
Despite winning their opening Group F game 4-0 against Maccabi Tel Aviv, the London side were beaten in Portugal by Andre Andre's strike and Maicon's header, in between Willian's brilliant free-kick.
Chelsea are third in Group G, a point behind Porto and Dynamo Kiev.
They are also struggling in the Premier League, lying in 15th place, eight points behind leaders Manchester United.
Mourinho, who described his side's first-half display against Newcastle at the weekend as "minus one out of 10", was pleased he "got a performance" against Porto, who he managed from 2002-04.
"When the game is under control we concede a goal that is ridiculous," said Mourinho.
"They hit the post from a similar mistake. Apart from that the game was balanced. Two ridiculous moments and we were punished.
"The team played well and there were good reactions from the goals we conceded. We had chances to equalise and had desire.
"When you feel everything is going against you it is disappointing. The team tried until the end so I have nothing to say against them."
'No problems with anyone'
Last year's PFA player of the year Eden Hazard was dropped to bench in Porto, while defenders Branislav Ivanovic and John Terry, midfielder Nemanja Matic and striker Diego Costa did not start the opening group game.
However, Mourinho says everything is fine at Stamford Bridge and his side can still reach the knockout stages.
"I have no problems with anyone and have a fantastic relationship with everyone," he said.
"We are third in this moment with three points and have another difficult match against Dynamo Kiev coming up. We have matches at home and we think we can qualify."