Barca won 1-0 in Monjuic thanks to Robert Lewandowski's first-half penalty.
Afterwards, Batalla lamented: "I think it was a very complex match against a rival, we played very well. Both teams had very clear chances. We were uncertain, I'm very happy with the team's sacrifice. We can feel proud.
"I don't like to talk about refereeing. I'll see about it later. I don't want to talk, out of respect, not out of fear of the consequences."
Rayo teammate Pep Chavarria added, "We're going away screwed. We could have gotten something out of this game. Well, again controversial actions where we don't know what happened and little else.
"We played a great game. We worked very well. It's not easy to get chances here. It wasn't a day to be happy, we're going away screwed."