Manchester City boss 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 ever nights 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 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.
"The difference was not just the mistakes of the referee. I think we cannot play the way we played 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.
City fell behind within a minute to a firm Seydou Doumbia header and the same player struck again after Toure hit a fine free-kick equaliser.
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 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.
"We must first try to play against QPR (on Saturday), then we have the international break and then we are going to try to qualify for the next stage.
"It is more difficult but it is not impossible.
"It is very difficult to understand how we played so bad from the beginning.
"We were so nervous, we gave away two bad goals, we didn't play.
"It is difficult to know why. It was such a low performance from important players.
"It is a strange moment. It is not just this competition. In the last two weeks we are not playing.
"I don't understand why but we must find a reason because we must arrange a situation. It is a crisis of confidence.
"I don't think the sendings-off decided the match, it was in the first half when we weren't ourselves."
Pellegrini also revealed captain Vincent Kompany took a kick to the calf late in the game and would be assessed today.