Wolves defender Gary Breen has assured supporters that the players would do everything to make up for the FA Cup disappointment by securing a place in the play-offs.
And Ireland international Breen, aged 35, said the players had been left in no doubt how furious the supporters who had made the trip to Cardiff were by the team's lacklustre performance.
He said: "It is just disappointing that the cup for us is over. To go 2-0 down to anyone at any level is always difficult especially in a highly charged FA Cup game and we gave ourselves a mountain to climb.
"We have been told in no uncertain terms by our manager that that is not acceptable and as players we realise how much this match meant to our supporters and so we are bitterly disappointed that we let them down."
Breen added: "It is up to us now to prove we can come back and we need to get them (the fans) back on side. It is no good saying we need them to start cheering us, they will start cheering us when we start producing performances and we didn't produce one today."
Breen continued: "I haven't seen the goals back but I remember the ball being threaded through to Jody (Craddock) and he and Hasselbaink clashed for the first one and the ball seemed to stop and then one of their midfielders got in and calmly put it away.
"Then as a team you are just looking to stay in the game but of course the momentum was with the home team and they scored the second goal.
"The original pass looked off side I am not sure but it was a wonderful finish. It gave us a mountain to climb but made things comfortable for them and they were able to sit back."
He added: "This will now be a real testament to the young players' characters as we look to the home game with Scunthorpe on Tuesday. We have a lot of bridges to build with our supporters.
"They came here again in their numbers. These two sides are big rivals I know they are not local rivals at such but there is a bit of history between the two teams and we have let them down. We now have to put it right."
Breen said he fully understood the reaction of the crowd who heckled the players during their warm down and vented their frustration at manager Mick McCarthy.
He said: "That's football. There can be no hiding place. Our supporters are fantastic. When we are playing well they are like an extra man and they will cheer us.
"But when we play like that they are angry and rightly so. If I came down here and paid good money I wouldn't be happy. "
He insisted the team would now make amends by securing a place in the play-offs to reward the fans.
"We are not where we expected to be in the league either," he said. "We have no divine right to be up there but building on last year we have had some good young players come in.
"Whether they lack a bit of experience I don't know but there are still 14 games to go and we will be in the play-offs no doubt.
"Something has to give and I see our young players in training every day and they have got strong characters and they will bounce back."