The Chelsea stopper says he felt like a teenager again when the Spaniard arrived at the Etihad Stadium as he was learning so much.
Training under Pep Guardiola is like going to university, according to veteran goalkeeper Willy Caballero.
The Argentine worked under Guardiola at Manchester City before moving on to Chelsea, where he has recently received a contract extension.
And according to Caballero, at the Etihad, every day is a school day.
“Pep Guardiola is like going to university,” Caballero told TNT Sports.
“I spent a year with him at City, learning something new every day.
“On the playing field, watching videos or at any time, when he approaches you and explains things to you.
“He has no problem teaching someone at 34 years old, as I was, like someone who is 18. He is a great teacher.”
Caballero’s year under Guardiola was the last of his three seasons at Manchester City, having moved from Malaga in 2014.
He followed manager Manuel Pellegrini, who had made the same switch a year earlier.
Caballero only made 23 Premier League appearances for City but was a regular in the cups, memorably saving three penalties in the shoot-out win over Liverpool in the 2016 League Cup final.
“Manuel Pellegrini had convinced me to go with him to Manchester City,” he explained.
“I was doing very well at Malaga, but I accepted. He had promised to keep me as a starter in the cup, although in the league, the starter was Joe Hart, the England national team’s goalkeeper.
“We reached the final and we had to play it against Liverpool. There was a lot of pressure for Hart to start the game.
“But Pellegrini said, ‘I’d rather lose a title than lose my word.’ It kept me going and we won the cup.”
Caballero also spoke about his new contract at Chelsea, which will see him stay at Stamford Bridge until 2021.
“I really appreciate having renewed for another year with Chelsea at 38,” he said.
“I always look back because I had a hard time getting to where I am. When I started at Boca, as well as when I got to the national team, I felt it was the top of the mountain, but they turned me around and I had to start from scratch.
“I went back to the second division in Spain and it served to give value to what I have now.”