Chelsea manager Jose Mourinho accepted that he got his team selection badly wrong after his side were beaten 1-0 by Basel at the St Jakob-Park on Tuesday.
Mohamed Salah's solitary strike with three minutes remaining gave the Swiss champions their second win over the London club in this season's Champions League, although Chelsea still clinched their place in the last 16 thanks to Schalke's goalless draw with Steaua Bucharest in Romania.
That meant it was job done for Chelsea, who came to Switzerland with the aim of ensuring qualification with a game to spare in Group E, but Mourinho was unable to muster a smile after watching a substandard performance.
"We don't go through because we got a result, we go through because Schalke did not get a result, and for me it's not the same," said the Portuguese.
"In the end, we qualified, which is our first objective, and now we have the last match at home to get the result to finish first," he added, with Chelsea knowing that a win at home against Steaua on December 11 will guarantee them top spot and secure, in theory, an easier draw in the next round.
Tuesday 26 November
FC Basel 1-0 Chelsea
S Bucharest 0-0 Schalke
Arsenal 2-0 Marseille
B Dortmund 3-1 Napoli
FC Porto 1-1 Austria Vienna
Zenit St. P1-1 At Madrid
Ajax 2-1 Barcelona
Celtic 0-3 AC Milan
Mourinho was quick to praise Murat Yakin's Basel side for their display - which followed a 2-1 victory in London in September - but he acknowledged that his decision to make just one change to the team after Saturday's 3-0 win at West Ham was wrong.
"I want to praise Basel. They won because we were sleeping in the last minute. But they won also because they were the best team and deserved to win," said the former Real Madrid boss, who dropped Eden Hazard for Willian.
"I think from the first minute I was getting signs that my team was tired. My team paid the price today of the international week, where I was afraid of the reaction in the game against West Ham.
"Maybe because that game was so important for us, the whole team focused a lot, and everybody made a good individual and collective performance.
"Tonight we made a big mistake in the first second of the game, immediately. After that, we made mistakes defensively, we made mistakes with the ball, we lost easy passes, we lost every second ball, late decisions, people thinking late, and we finished with a ridiculous goal.
"It is not the kind of game where we are upset with the players, because I think I understood, and I maybe should have made more changes."
Chelsea begin a run of nine games in December with a home clash against Southampton in the English Premier League on Sunday, and new faces will come into the side for that game.
One man who looks certain to miss that encounter is Samuel Eto'o, who was stretchered off just before half-time following a clash with Basel midfielder Serey Die, with fit-again Fernando Torres taking his place.
"Samuel has a muscular injury. I don't know the dimension - we will have to wait to do scans - but it is a muscular injury," Mourinho said.
"This situation maybe helps me to make decisions when you have consecutive matches. I got signs that some players struggled to play two matches in three days so that will push me, for sure, to make different decisions. That is obvious."
Basel's recent record against English sides at the St Jakob-Park is impressive, with this latest win against Chelsea following victories over Manchester United and Tottenham Hotspur in Europe in the last two years.
Tuesday's success also means they are now in a position to qualify for the last 16 for the second time in three seasons, with a draw against Schalke in Germany next month all they now require.
"Everyone knew it would be historic for us if we could beat Chelsea twice, and I think we wouldn't have deserved just a draw," said Yakin.
"It will be a nice final match against Schalke. That is what we worked for and we will try to qualify for the knockout stages."
Even if Basel lose in Gelsenkirchen, they are guaranteed the consolation of dropping into the Europa League in the New Year.