Arsenal striker Olivier Giroud was left ruing his missed header in the second half against Barcelona, which he called "the turning point" in the 2-0 loss at the Emirates.
Giroud's best chance in the much-anticipated Champions League clash came in the 60th minute when he met a cross in the area to send a header toward goal while under pressure from Javier Mascherano.
But Barcelona goalkeeper Marc-Andre ter Stegen dove to his right to palm the ball away with his best save of the night. And 10 minutes later, Lionel Messi finished off a quick counter-attack to put the visitors ahead in the first leg of their round-of-16 meeting.
"It's maybe the turning point," Giroud said about his header. "The keeper did well. I have a duel with a defender, and I think I headed the ball well, but the keeper did very well. And then on the counter-attack we were not maybe cautious enough. It was a model of a counter-attack and Messi finished it well."
The loss left Giroud and his teammates feeling frustrated after holding their own for the first 70 minutes, and also missing a couple of good chances to score in the first half.
"We played well on the counter-attack and were dangerous. But we couldn't finish the work. It's a shame," Giroud said. "We can have regrets tonight because we didn't finish our good counter-attacks. And we were punished at the end of the game."
Messi added his second goal with a late penalty after he was brought down in the area by Mathieu Flamini following a mistake by Per Mertesacker, leaving Arsenal with a nearly impossible task to overturn the deficit at the Camp Nou. The Gunners now look likely to exit the Champions League in the round of 16 for the sixth year in a row.
"I think 1-0, it was OK, we could have a chance even if it's still hard. But 2-0, it's a shame. It's a bit disappointing," Giroud said.
"It seemed like we caused them a lot of trouble in the first half. We could have scored one or two goals. We didn't finish the job. At this level, if you don't score, Barcelona will not miss. Even if Petr Cech did very well in front of Neymar, you know they will do it if they get several chances to score. But I regret a lot this penalty at the end of the game."