Following a 1-1 draw in the first leg at Camp Nou, Koke's early volley earned Atletico Madrid a 1-0 win that took them into the last four of Europe's top club competition for the first time in 40 years.
Lionel Messi and Neymar missed a couple of good chances for Barcelona, and despite Atletico having several opportunities to increase their lead and hitting the woodwork three times, Xavi believes the visitors were worthy of a draw at the Vicente Calderon.
"I do not know if Atletico deserved this win," the Spain midfielder said.
"We have had several chances to get the draw. We had four or five chances that usually we score. I think we deserved the draw, sending the game into overtime."
Barca coach Gerardo Martino praised Atletico for containing his side, and hailed the hosts' fans for the incredible atmosphere in the capital.
"When Atletico were the better side, they scored their goal," he said.
"We also had opportunities and just one goal from us would have changed the course of the game.
"At certain points, we couldn't do the things (we wanted) because of how our opponents played.
"Atletico kept a lot of players near their penalty area – they did that very well and that made it hard for us to find any space.
"This atmosphere is difficult to find in Europe, but it's more common in Argentina. Results happen for a reason though."
"We have to keep fighting in the two competitions that remain for us now: the league and the Copa del Rey."
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