Arsene Wenger revealed goalkeeper Wojciech Szczesny and centre-half Laurent Koscielny were left "destroyed'' after their last-minute mix-up cost Arsenal the chance of Carling Cup glory and gifted Birmingham a famous 2-1 victory at Wembley.
Extra-time was looming when Szczesny spilled a long punt from Ben Foster after Koscielny's mis-kick and substitute Obafemi Martins slotted home in front of the Blues fans to send the Midlands club into Europe as Wenger's quest for a first trophy in six years went on.
It was, though, no more than the Blues deserved following a battling display as Arsenal, without injured captain Cesc Fabregas and England winger Theo Walcott, once more failed to deliver when it mattered most.
"Both of them [Koscielny and Szczesny] are destroyed,'' said Wenger, "We have to lift them up again and help them, that is what a team is about, that is part of the game.''
On the costly mistake, Wenger said: "It was a lack of communication, determination a little bit as well. Like always, when the ball is in no-man's land, someone has to take responsibility and go for it. What was amazing [was that] no-one was going for the ball from Birmingham.
"I am bitterly disappointed, like the whole team. We had some problems to start the game, the number of games we played caught up a little bit on us. It took us a while to get into the rhythm and pace of the game.
"In the second half we were on top, unfortunately we couldn't score the second goal and, in the end, we made a mistake that left us no time at all to respond.''
Arsenal were crestfallen at the final whistle, but Wenger must now lift his side for an FA Cup fifth-round replay against Leyton Orient before the return leg of their European tie in the Nou Camp to ensure another season which promises so much does not once more end in bitter disappointment all round.
"Congratulations to Birmingham, they took advantage of the mistake [and] they took the trophy which hurts us tremendously,'' said Wenger. "We have to be proud of our attitude, continue with our belief, pick ourselves up and face the other challenges we have.
"We will face a lot of questions after that mistake tonight, but we have to be strong enough to stand up. It is a good opportunity to show that we have the mental strength to respond to the situation like that.
"It is a massive disappointment for the team, but we have massive challenges in front of us - the Carling Cup is four games, five games but a championship season is 38. We will not throw 38 games away because of one game.
"I am confident we have the character and this is a good opportunity to show it.''
Centre-half Johan Djourou insists all is not yet lost for Arsenal this season, and challenged his team-mates to show the character of champions over the remainder of the campaign.
"We just could not get that second goal to win us the Carling Cup today, but we have other things coming up,'' said the Switzerland international. "We are still in the FA Cup, there is still the League and the Champions League, so we need to bounce back.
"We are aiming to get back to Wembley in the FA Cup & also the Champions League. The club needs to show character now and we have the resources to do it.''
On the costly mix-up between his defensive partner and goalkeeper, Djourou said: "Things like that happen in football. It is just a shame it happened so near the end - but also mistakes make you stronger.''
Fabregas said on his Twitter page shortly after the end of the game: "Congratulations to Birmingham. This team has great potential and there r still great targets to play for this season. Thanks for ur support."
Van Persie also tweeted: "I'm very sorry that we didn't bring CC back to north london! Thanks for ur support today! Sorry again!"
And Jack Wilshere also said: "All i can say is sorry to the fans ... it hurts alot i know but we must all stick together, still in 3 other comps! We have to move on! Sorry."
Another tweet from Samir Nasri stated: "Thank you for your support guys its a massive blow but we have to look forward wednesday FA Cup and we have still 3 competition so chin up."
However, full-back Bacary Sagna could not hide his disappointment, simply saying: "Just feel ashamed. Sorry.''