Pep Guardiola has revealed his debt of gratitude to Ronald Koeman as the pair prepare to do battle as managers on Saturday.
The two old friends meet as equals at the Etihad this weekend as Koeman's Everton aim to make it a third straight game without a win for Guardiola's Manchester City.
But there was a time at Barcelona in the early 1990s when Guardiola, then a novice midfielder in the same side as European Championship-winning defender Koeman, was very much the junior partner.
"When Ronald needed water, he'd wake up to water from me," the City boss said. "I was younger so I looked up to him.
"He was not just a roommate, we spent a lot of time together and he was so generous. Not just on the pitch but off it too - I learned a lot from looking at him.
"He was one of the first central defenders with the quality not just to defend. I think Johan Cruyff bought him to teach us why we needed a central defender like Ronald. He was one of the few guys who I never saw miss an important game.
"He always played good in the big games. Against Real Madrid, in the Champions League, he was amazing. He's one of the best central defenders I've met in my entire life."
Another ball-playing centre-half, John Stones, has warned Guardiola of the threat his former club will pose on Saturday.
"John told me how good they are, the quality of the players - he was one month, two months with Ronald - not a long time," Guardiola said.
"He played with five in the first game against Tottenham, sometimes 4-4-2, sometimes 4-5-1. I don't know what Ronald will do on Saturday."
Guardiola is sometimes pigeon-holed as a possession obsessive, but while the fundamentals of his philosophy are not up for debate, the Catalan insists he is enjoying the challenge of bending his style to suit the Premier League.
"At every stage, every club, every country has its own specific things and you have to adapt and adjust," he said. "I played in different styles against different problems the opponents created in the last seven years and that's beautiful.
"The way I want the players to win the game is the way I believe. At Barcelona, we were a very good team but during the season maybe we crossed ten times in a whole season. We attacked a lot in the middle for the quality we had at that moment.
"At Munich, it was completely different, we had a big striker and amazing wingers - the way you play depends on the players. But the fundamentals are the same."