Manchester City manager Manuel Pellegrini offered no excuses after his nine-man team slumped to a dismal 2-1 Champions League loss to CSKA Moscow.
Midfielders Fernandinho and Yaya Toure were both sent off as City suffered one of their worst nights in four seasons of playing in the competition.
Pellegrini might have had reason to complain about the dismissal of Fernandinho as well as two rejected late Sergio Aguero penalty appeals, but he accepted that his team had again failed to deliver.
The result leaves City bottom of Group E with just two points and facing a mountain to climb to reach the next stage with remaining games against Bayern Munich and Roma.
Asked for his opinions on the moments of controversy, Pellegrini said: "I think it is not my duty to analyse the referee's performance. It is your duty to decide if he made a good decision or bad decision.
"Today the difference was not just the mistakes of the referee. I think we cannot play the way we played today if we want to win.
"I don't want to have any excuse about the way we played. That's why I don't want to link the referee with the result."
City had gone into the game with some optimism after ending a three-game winless streak with a morale-boosting derby win over Manchester United at the weekend.
But their familiar problems in Europe again came to the fore and Pellegrini was puzzled by the lack of spark from his side.
Pellegrini said: "It is difficult to understand why we played so low a performance. We have just played a good game here against Manchester United.
"We have all our chances to win here at home and play a normal way but when you give two easy goals in the first half and you really don't play with the ball, it is very difficult to win.
"We are in a bad moment with the performance but the only way is to try and arrange is to continue working and work out why there is a lack of trust with the players.
"Normally we are a very disciplined team so for me it is more important we return to our normal performance."
Pellegrini refused to rule out the possibility that his team could still qualify for the last 16.
The Chilean said: "If you have the mathematical option to qualify, you must fight for them. We must first try to play against QPR, then we are going to try to qualify for the next stage. It is more difficult but it is not impossible."
Pellegrini also revealed that captain Vincent Kompany took a kick to the calf late in the game and would be assessed today.
Worryingly for City, they now must beat Bayern Munich who set a German record for the quickest Champions League knockout stage qualification - and coach Pep Guardiola thinks his team are yet to hit top form.
Bayern cruised through to the round of 16 with their fourth win in four games and two games to spare. Unbeaten in 16 matches in all competitions this season, Bayern have let in just one goal in the Champions League, in their 7-1 record away win in Rome.
"No, not yet," said Guardiola, in his second season at Bayern. "We are playing better than last year but we have to improve.
"Obviously we are playing better. We talk a lot, we have a lot of meetings, but we can always improve, always, always."
Guardiola said at the start of the season that his team, sprinkled with more than a dozen internationals, would need time after the World Cup disrupted their preparations.
"I did not expect to be in this position after the World Cup," Guardiola said. "The players are always eager to play."
The Bavarians were never threatened by Roma and scored once in each half through Franck Ribery and Mario Goetze.
This was Ribery's second start of the season following a lengthy injury absence. "He is playing better and better," Guardiola said.