Arsenal boss Arsene Wenger accused his players of being "naive" after letting Barcelona hit them on the counter-attack to take a 2-0 advantage after the first leg of the Champions League tie.
After largely containing Barcelona's powerful attack, Arsenal pushed forward in search of a winner in the second half only to allow a lightning counter that was coolly finished off by Lionel Messi in the 71st minute. Messi then added a penalty in the 84th after poor defending from the Gunners resulted in substitute Mathieu Flamini bringing the star forward down in the area.
Arsenal are now staring at elimination in the round of 16 for the sixth year running, and Wenger said his team made the same mistake as against Monaco in the first leg last season when they pushed forward for a late equaliser and allowed a late goal to go down 3-1.
"The regret I have is that once we looked like we could dominate the game in the last 15 minutes we gave the goal away," Wenger told BT Sport. "It was similar to Monaco. Naive. And that's what's frustrating. Because when it looked like we could win this game, we just gave it away."
In his postgame news conference, Wenger added: "I feel that we were extremely guilty and have no excuses for that goal.
"The players didn't give them a counter-attack on purpose. They want to defend it. It's just that the first pass is not right, the first position is not right, you lose the ball when you don't want to lose it and then suddenly you're out of position and they take advantage of that.
"It's not because the players do not want to respect the instructions, they were just caught by the pace of the game. It was an unexpected wrong pass or unexpected position of the first play."
Wenger had warned about Barcelona's threat on the counter before the game, saying they are at their most dangerous in transition. He was proven right as Neymar and Luis Suarez combined to race down the field before Neymar found a wide open Messi in the area.
"We knew before the game that the one thing we could not afford is to give them counter-attacks, because they are very dangerous. And that is exactly what we did," Wenger said.
"We pushed too far into their half and we got caught. I knew in the last 20 minutes we'd have a chance to win the game if we didn't make any mistakes, and that is the frustration of the night."
Wenger praised his team's effort and energy but said that "technically we were very average overall."
"When your players put in the energy that they have put in tonight, it's very difficult to take because you want the players to be rewarded," Wenger said. "We were impatient in the build-up, we lost balls that we usually don't and that's not because Barcelona forced us to do it, but just because we were not precise enough in our passing. ...
"We had an unbelievable chance in the first half [through Alex Oxlade-Chamberlain]. The way we finished our chances today is a problem because I felt that we missed something in the final third."
Wenger assessed his team's chances of overturning the deficit at about five percent, saying that it will be "realistically really difficult, if not impossible."
"But we have to go there and fight," Wenger added. "We have to have a go. And we want to show that we can beat them, and you never know."
