Real Madrid won 1-0 through Gonzalo Garcia's goal setup by Trent Alexander-Arnold.
Xabi said afterwards: “We have to do a lot with a little. We've only been together a short time and we're competing for big things. We had to adjust things and the guys have grasped this well.
"We were getting more and more in the opposition's half and we had to be patient. Unfortunately, we failed to find the second goal that would have given us the margin, but it's Juventus and we have to compete. We had to grit our teeth at the end.”
“Defensive solidity and discipline are fundamental and something we've tried to transmit from the start. The lads are eager and willing and that's essential. They're keen to absorb what the people who have come from Germany are asking of them.”
Gonzalo and Trent performances
On Gonzalo, he said: “I'm not going to go into the next day's preparation. I'm pleased for him and for the team. We've progressed. These players are used to playing in the ties, but not in this new stage. I'm happy for everyone.”
Asked about Alexander-Arnold's performance, Xabi stated: "We were caught out by (Kenan) Yildiz's position in the middle. Everything takes time, but I have faith in him. He's a reliable full-back and so is (Dani) Carvajal.
"We will improve from the collective side to the individual and not the other way around.”