Samir Nasri has admitted that the 2-1 defeat to Wigan Athletic on Sunday was a body blow to Manchester City as they felt that the FA Cup was theirs to lose.
The Citizens toiled again at the hands of the Latics, who shocked them in last year's final at Wembley, when they lost in the competition's quarter-finals at Eastlands.
Nasri has claimed that City had the FA Cup "on a plate" and threw it away, but has said that they are now determined to respond to the setback when they attempt an unlikely turnaround against Barcelona in their Champions League last-16 tie on Wednesday.
Asked how he felt after the Wigan result, Nasri told reporters: "Hungover. It was a bad performance, we didn't play well.
"The big disappointment is that it is twice now that Wigan have beaten us in the FA Cup. It is really difficult to accept. It is like - the FA Cup, they gave it us on a plate and we refused to take it.
"I really don't know. I cannot find the words because I am really disappointed. Thank God we play a big game on Wednesday. It is the best way to forget this game and be focused on the next one. At training we are going to think Barcelona and try to think positive and get a result there."
City trail 2-0 to the Catalan giants following the first leg at the Etihad Stadium a fortnight ago.
