The 25 year old Spaniard has regained his spot as Klopp's first-choice left-back this season, having made only two Premier League starts last term.
Klopp told the club's website: "I never had something like this. I never had it to be honest.
"This season is not a surprise; the surprise is how (he) dealt with last season. There was not one bad word in the whole season.
"Yes, he was in my office. Yes, he asked what he could do better, and we spoke about the things he had to do better.
"On the other hand, Milly (James Milner) played really well and he's a machine. He could play every two days, so there was not a lot of reasons to make the change then - he had no rhythm.
"I felt that it was unfair after the season. I thought 'damn, we didn't use him often enough'.
"Before the season, he came to my office and asked again, and I told him we (would) get another full-back, but it was not the plan for Milly to be in the full-back race again, so you decide what happens - and he decided it.
"How he reacted on last year is really, really good. He's now a much better defender. That's how it is; he's a brilliant footballer.
"When you see him shooting here, you think he cannot shoot - he shoots like crazy. It's unbelievable how good he is. In the games so far, obviously, it didn't settle."