Gonzalo Garcia fired Real ahead before Ruben Neves beat Courtois from the penalty spot. Bono then saved Fede Valverde's penalty to keep the scores level.
Xabi later said: “The second half was considerably better than the first. We were lacking in several areas in the first period, both with and without the ball. We were losing the ball too quickly, we couldn't find a balance. They're things we have talked about but we took a while to get to grips with them.
"I'm pleased with the reaction at half-time. We managed to give a new look to the game, change the pace a bit and find more guys to bring the right rhythm and control to the play.
"That helped us get in good positions around the opposition box, adjust our press, and we spent more time near their area. This is a process. Everything takes time. The first half wasn't very good but we have to take the positives and look at how we can learn from the negatives.”
Thrilled for debuting pair
On the debuts of defensive pair Trent Alexander-Arnold and Dean Huijsen, Xabi continued: “First I'd like to congratulate them, because this is a big day for them. Making a Real Madrid debut will surely have an impact on them. I'm thrilled because they have that personality and they'll be important players for us. Having them here will give us added quality."
On the overall performance, the coach also said: “We had no doubts about it, we knew all along. Whoever thought it was all going to fit perfectly into place... We knew which elements would work well and which we'll need to keep working on in order to improve. When we showed better quality on the ball and more control, we imposed our will on the game. We didn't manage to do that in the first half.
“It's not frustration. We know this is going to take time. In fact, I saw a reaction in the second half. We started doing better at the things we've spoken about. Everything takes time, it's about repetition until it sinks in. We've been together for 9 days, barely three training sessions, and this is a process. Of course, we have to get results because this is a competition, but we also want to learn and understand what we want to be."