Herrera left United for Paris this summer after coming off contract and admits the commercial aspect of his old club left him cold.
He told So Foot: "Since I've been here, what I'm seeing is that I'm in a club that thinks exclusively and only exclusively about football.
"It was not the case in Manchester? I was very happy in this incredible club. I am very grateful to his supporters. Frankly, I was immensely happy in Manchester, but in the club, there were times, where I felt that football was not considered the most important thing.
"Was business important then? That does not come out of my mouth, I do not know, but football was not the most important thing in Manchester. I do not want to compare, all I know is that here, I feel like breathing football on all sides. And I like that."