The Andalusians missed a number of opportunities to take the lead before falling behind, but once they were trailing there was only going to be one winner.
"Devastating and undeserved," was how Lopetegui described the result.
"We did things very well, we were brave in our approach and we tried to do things that we worked on."
Luuk de Jong was guilty of passing up four chances, three of which came at 0-0.
"De Jong did a lot well," Lopetegui said in defence of his forward.
"But to win at the Camp Nou you have to do things very well and also have a bit of luck."