Real won 2-1 thanks to goals from Kylian Mbappe and Rodrygo, who hit a winner after Carlos Vicente had equalised for the hosts.
One of the talking points was a penalty call for Vinicius Jr in the second-half, which was waved away - including by VAR.
After the win, Xabi said: "It was a very competitive match. We started very well. Then we lost control a bit. We started the second half well, but we conceded a goal on the only play Valdepeñas made, because they played very well.
"The team showed character. The second goal gave us the three points. We're happy with the three points, because the important thing was to win."
On the penalty, he said: "The action seemed clear to me. I'm surprised it wasn't reviewed by VAR. We have to move on. Although it doesn't surprise us."
On VAR Pablo González Fuertes, Xabi added: "We'll leave it at that."
He then said: "We all like it better than the Celta game. There are things to improve. We need consistency. If it serves as a learning experience, hopefully it won't be forgotten.
"There's no common pattern in the matches between Celta, City, and today's game.
"We are very focused on our own game. I give a lot of credit to the victory considering the absences we had. We are all together. This isn't just one game. There's still a long way to go. Unity is fundamental."