The Portuguese icon rejoined United in 2021 under Ole Gunnar Solskjaer, enjoying a prolific first season with 24 goals.
However, his second campaign under Ten Hag was far less effective, leading to tensions and his eventual exit.
Speaking to Ladbrokes, ex-United assistant Benni McCarthy said: "Erik wanted pressing from the start.
“And I think Ronaldo, when he came to United, in his early years at Real Madrid, he was able to do what Erik expected him to do, like high press and then still have enough in the tank to get himself into positions to score.
"So Ronaldo was varying his game a lot, but it wasn't how Erik wanted to play. So he felt that it just couldn't work.
"Having Cris in the starting XI wouldn’t work with the way we wanted to play, and that's why Erik preferred Anthony Martial."