Hummels came up against Balotelli in this week's Champions League clash.
"Balotelli has a special meaning for me, my brother and my friends,” said Hummels, who swapped shirts with Balotelli after the match.
"I've had the order to get a shirt from him for two years. It did not work out after the first match and after the Euro semi-final when he scored twice against I had other things on my mind.
"He's a favourite in our group of friends. We think he's a cool guy, a great player. I don't believe that all the stories you hear about him, are that bad."