Celta managed to edge the tie 3-2 thanks to a late Racing own goal.
Giraldez said afterwards: “We knew it was going to be a very complex match and that it was going to be very difficult for us, against a team that, for me, is at Primera level in terms of players, fans, history, coach... I think we had the key in the first half to do much more damage against the defence of four of them.
"We were not precise in the last phase and in the final stages and they caught us in 2 or 3 transitional actions with our losses being a bit childish.
The desire to progress to the next round, to have a chance in this competition, made us end up winning and overcoming many obstacles during the match, which was not all that good.”
On an injury to Iago Aspas, Giraldez is hopeful it is only minor: “It's a shame, in those moments with a tight defence he is our most talented player in that final pass, in that creativity.
"He has a problem in his calf that has become hard, let's hope it's nothing. He is intelligent and he wanted to stop at that moment.”