The Brazilian will be starting for United against City in the showpiece domestic cup final on Saturday.
As the two sides prepare for the game, and City chase a history-equalling treble of trophies, Guardiola took out time to praise the former Real Madrid anchorman.
“I don't know him but I had info when he was in Madrid; how professional he was, the quality he has," Guardiola told reporters on Friday.
“I was convinced he wasn't coming here just for his holidays or the last years of his career.
“When you've won four or five Champions Leagues with Real Madrid it's because you are special player. Otherwise you cannot be there for a long time."