After captaining City to a Treble, Gundogan left for Barcelona a year ago.
Guardiola says the German is one of the best players he's worked with.
He told Mundo Deportivo: "İlkay didn’t talk much, but when he did, everyone listened to him, including me as a coach. He was clear and direct. He is a very intelligent player, one of the most intelligent players I have ever coached. He was the key to our success,.
“A player can be fast, he can have a good shot, but what makes him stand out from the rest and become an elite player is his intelligence. Making the right decisions under pressure, knowing what the team needs at all times, that’s the type of player I’m looking for.
"I love smart players. I only had to explain everything to İlkay once. He understood it and put it into practice immediately. That is extraordinary.”