There are concerns that he won't be able to compete for the biggest trophies at the club and that's why he wants to leave.
The 37-year-old feels the urge to win more in the twilight of his career, but may not be able to do that at Old United.
United are yet to make any additions to their squad in the current transfer window, and that is something thatRonaldo is worried about.
The player is said to be very fond of the club and respects the fans a lot.
This will be the first time in his career that he won't play in the playoffs if he stays at Manchester United.
United are trying to bring in players for the new manager, so they don't wantRonaldo to leave.
They want to sign Frenkie de Jong from Barcelona, and they also want to sign Lisandro Martinez from Amsterdam.
In August of last year,Ronaldo re-signed for United in a deal worth over twenty million dollars.
He was frustrated as the team failed to finish in the top six.
Sky Sports News asked Manchester United about something.
The majority of United's transfer business needs to be done before the squad leaves for their pre-season tour.
The club has a basic agreement in place for Barcelona's Frenkie de Jong, and is close to completing a deal for Feyenoord's Tyrell Malacia.
United are very interested in the situation of Lisandro Martinez and have been doing due diligence on the situation, while Christian Eriksen is making a decision on whether to accept an offer from United or stay at the club. The former Spurs player remains open to other proposals.
The new side of Ten Hag is in talks with his old club about Antony, but they don't think he'll stay. The centre-back was on a list of defensive targets.
Steve Brown is the head of recruitment operations and John Murtough is the football director. The brother of a former United player has been hired as a consultant to draft deals.
The transfer window will open on June 10 and close at 11pm on September 1st.
Sky Sports has a dedicated Transfer Centre website where you can keep up-to-date with all the latest news. Sky Sports News gives you the ins, outs and analysis of sports.