Martin O'Neill preferred to highlight Celtic's growing stature in Europe than dwell on defeat to Villarreal.
"It shows how far we have come in the last few seasons that we are disappointed to lose in the Uefa Cup quarter-finals," said the Celtic boss.
"Expectations are now very high at the football club after reaching the final last season.
"We conceded a poor early goal, but we play as a team and we just missed that sparkle that would turn the tie."
Hesitation by Bobo Balde allowed Sonny Anderson to put Villarreal 2-1 ahead on aggregate and Roger killed the tie after the break.
"Losing that early goal put us on the back foot," said O'Neill.
"But then we had control of the game and I was pleased with the effort shown.
"In the second half, we had to go for it and, if we concede a second goal, you always run that risk."
Celtic lacked the goal threat of striker Chris Sutton, who failed a late fitness test, while influential midfielder Alan Thompson was suspended.
"They were obviously missed tonight, but that's just the way it goes," said O'Neill.
Celtic captain Jackie McNamara, who was voted BBC Scotland man of the match, refused to use the missing personnel as an excuse.
"It is a big loss not having Thommo and Sutton, but I still thought we could win here," he said.
"We lost two bad goals from our point of view, but we had a spell when I thought we could come back into it."
Defeat to Villarreal came after victory over more renowned Spanish opposition in the previous round.
"We knew it was going to be hard, as they are a good side," added McNamara.
"But they are not better than Barcelona and I thought we could have won here."
Celtic's disappointment was tempered slightly by the news that Rangers' draw with Livingston means that the Parkhead outfit can clinch the Scottish title at the weekend - and, with it, a place in the Champions League group stages next season.
Villarreal coach Paquito had a semi-final against local rivals Valencia to look forward to following a campaign that started in the Intertoto Cup.
"It's a dream to reach the semi-finals," he said.
"We're very happy and I congratulate both sets of supporters.
"Either team would have been a just winner. It was amazing to see how both groups of fans enjoyed themselves."