Rooney was speaking about the title race during an appearance on the Sky Sports program Monday Night Football.
He had praise for his former side under Jose Mourinho, but says their work is cut out given City's form this season.
"In terms of catching Manchester City, they certainly won't this season, but, if I am being perfectly honest, it will be difficult to catch them next season," Rooney said.
"City are getting to the level Barcelona were at four or five years ago. It is not nice for me to say, but it is almost perfect football at times.
"Guardiola is putting the foundations in place to try to emulate that Barcelona team, and they are well on their way to do that. Another one or two players coming in this summer, and I don't think they are that far away."