The Ivorian spent three years at Camp Nou, where he says he learned a lot and made many friends, before making the move to Manchester.
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"It's difficult because I don't really want to play Barcelona. It's a club I have a lot of respect for, a club which taught me a lot and where I have many friends who helped me," the 30-year-old told Uefa.com.
"I will play against these guys at the Camp Nou. It's the stadium where I always wanted to play and now I'll be coming back wearing a different shirt.
"I didn't want to play in front of the fans who gave me so much love and respected me but that's football."
Toure does admit, however, that he has enjoyed a more expansive role since joining City, especially as he prefers the "fast-paced" style of English football.
"At Barcelona it was my job to hold and organise," he added. "It was all about being focused and never losing concentration.
"Now I can drop into defence or join the attack. I was limited to playing in the middle at Barcelona. I like playing in England because it's an open league and very fast-paced.
"We have a great desire to show our fans and everyone else that City are on the right track."