Jurgen Klopp saluted the "incredible performance" of Adrian despite a lack of preparation time as the goalkeeper's shootout heroics won Liverpool the UEFA Super Cup against Chelsea in Istanbul.
The Spaniard denied Tammy Abraham in the shootout with a trailing leg in the 5-4 victory on penalties at Vodafone Park, with the match level at 2-2 after extra time.
A few weeks ago, Adrian was training with semi-professional side UD Pilas in his country's sixth tier to keep in shape following his release by West Ham United.
He was on the verge of joining Real Valladolid before Liverpool made him an offer to deputise for Alisson as Simon Mignolet joined Club Brugge.
The European champions expected the 32-year-old to have an extended adjustment period following his signing on Aug. 5, but those plans were derailed on the opening day of the Premier League season when Alisson limped off with a calf injury in a win over Norwich.
Klopp saluted the player's big "personality" as a factor in why he has settled so quickly and performed so admirably for Liverpool despite his competitive inactivity.
"He played an incredible game, he had sensational saves," the manager said. "Both goalies had that, but maybe from Adrian it's a bit more surprising because it was without pretty much any preparation. I don't know when he played the last game for West Ham, to be honest, so it's a while ago. Being ready like he was ready tonight is incredible.
"He's not only on the pitch a great person, he showed me already that he's a proper personality in the dressing room as well. He was maybe louder than I was at half-time. I was not loud because I wanted to give some information, but he was really on his toes and that was good. It's important and it helps us. He deserves that.
"Of course in penalty shootouts it's always lucky, but his performance over the 120 minutes was incredible. Making the save for the penalty is the icing on the cake and is wonderful. I saw now one time that he could really grab his towel before he started celebrating. That's special as well, so he's obviously quick in mind and knows what he wants to do. He helped us a lot and he can be really proud of what he did tonight."
Adrian, who last started a game in January while at West Ham, was adjudged to have impeded Abraham in the box during extra time by referee Stephanie Frappart, with Jorginho converting the penalty to take the contest to a shootout.
Klopp did not agree with the decision, but applauded the officiating of the Frenchwoman and her assistants Manuela Nicolosi and Michelle O'Neill after Frappart became the first female ref to take charge of a major UEFA men's competition on Wednesday.
"I told the refereeing team after the game that if we would have played like they whistled, we would have won 6-0," Klopp said. "That was my absolute opinion.
"They reffed a brilliant game. I told her as well that I am not happy with the penalty decision because I'm still not sure that it was a penalty, but it's not important anymore. They were really good.
"Whatever you could have thought before the game, there was pressure on them like hell with an historic moment. Staying calm and do what you have to do, decide very important things in a very difficult and intense game -- I couldn't have more respect, to be honest. It was really a brilliant performance."