"We are disappointed with the manner of the defeat. I don't know how many times we gave away 50 or 60 metres in the first half and we made it too easy for them to make territory," admitted Kellock.
"At times we needed to keep it tight, but there weren't too many line outs in the game. That was possibly a tactic from the Blues and it stooped us getting some drive into the game.
"But we also needed to release the backs as well to be able to put pressure on them out wide. I thought they defended us very well.
"For years I've been saying we need to step up when we come into this tournament and at times with some of the stuff we did we took that step forward. But in a lot of things we did we were well off and if we don't fix it quickly then it will be the same result next week.
"We haven't been great at Scotstoun in the last few games, so we have got a point to prove -not just to ourselves but to our fans."
Kellock's words were mirrored by a bitterly disappointed Warriors head coach Gregor Townsend.
"Cardiff showed what a good team they are and they also showed how much they wanted it. We've got to do that next week and more - we simply need to produce a better performance next week," said Townsend.
"I thought we played pretty well for the first 15 minutes, but couldn't get points on the board. Then they got their tails up, but we still had the belief to play better in the second half.
"In the first half we didn't work hard enough in attack. You have to go through the phases and we were trying to go too soon. We couldn't get much momentum in the set-pieces and that makes it difficult to get your game going."
A delighted Blues head coach Phil Davies was full of praise for his young side - Welsh internationals Sam Warburton, Matthew Rees, Bradley Davies, Lou Reed, Andries Pretorius, Owen Williams, Gavin Evans and Cory Allen were all missing through injury - but is expecting a severe backlash from Glasgow next week.
"Glasgow are a top side and they'll be champing at the bit. We've got to be ready for that - we're going to have to do what we did tonight and then some more at Scotstoun," dmitted Davies.
"After all the painful times we've had over the last 18 months, we're making progress. We're trying to build a style of playing here whoever is available and it's coming along."