Manager Jose Mourinho refused to blame his players for a "bad performance" as a 1-0 defeat at Basel still proved enough to send Chelsea into the Champions League knockout stages.
Mourinho blamed tiredness amongst his players for the defeat and admitted he should have made more than the one change he opted for from the side that won 3-0 at West Ham on Saturday.
Willian was the only player to come into the starting XI, at the expense of Eden Hazard, as Mohamed Salah's 87th-minute strike was the difference.
"I felt they were tired," Mourinho told Sky Sports 2.
"I think after West Ham maybe they paid the price.
"The players were tired. I'm not so sad with them. I understand.
"Maybe I should make more changes with my team. When you have that performance against West Ham you have the temptation to play the same team.
"I made one change with Eden because I felt he could come on and change the game. Maybe I should change other players."
A goalless draw between Steaua Bucharest and Schalke meant the Blues still went through, which Mourinho conceded was the only positive from the night.
"It was a bad performance," he said.
"Only because of other results we have qualified. That's the only positive thing from this night."
Asked what went wrong Mourinho, who saw his side beaten 2-1 by Basle on the opening night, added: "Everything. I didn't like it from the first minutes when immediately we made a defensive mistake.
"We should get a better result than this. I just want to prepare for the weekend.
"I don't want to blame the players."