Raphinha, Robert Lewandowski and Eric Garcia struck the goals as Barça made it 10 points from 12 in LaLiga so far this season.
Xav said, "The balance is really positive. It was a difficult start for the first 15 minutes, but then we settled in the game. We began to circulate the ball better. We played in their half but we also created chances in transitions.
"It was a good performance, I think we dominated and could have scored more goals. The dynamic is good and we must take advantage of the good moment of form we are in."
On Gavi, he added: "I am not surprised by Gavi's performance because I see him train every day. I know what he's capable of. The way he plays, he is pure intensity, personality, hard work, heart, discipline (...) I don't want to be unfair on the others, but he was perhaps the best player tonight."