The former City defender impressed against his old club in Saints' 1-0 defeat.
Guardiola later said: “I’m so happy for him because he’s a lovely guy.
“I’m happy that he’s settling in the Premier League. He’s an incredible threat for Southampton from set pieces and a composer when they have the ball because the manager insists the way they have to play, they have to be close, to move differently,
“They have a different way of playing through the lines. Aaron Ramsdale was magnificent with the ball.
“How good they link inside and lateral balls. I showed many images to the team and warned them. I said: ‘Guys you have to feel that at the right moment you will do good things with the ball and you have to be strong and you have to continue because they are good.’”