The last time that the 37-year-old player appeared for United was at their 4-0 defeat in Brighton in May.
Although the teams overall campaign last season was seen as a disappointment, Ronaldo remained the clubs top scorer. However, they still managed to miss out on the Champions League and only finished in sixth place in the Premier League.
This now means that Rolando faces the likelihood of playing in the Europa League and this is not sitting well with the Portuguese forward. He only has a year left with United plus an optional year.
The five-time Ballon dOr winner is now looking for other more attractive options.
He stresses that he has much respect for United but as he enters the final years of his career, he wants to play for the biggest prizes.
It would be a blow for Manchester United to lose Ronaldo but it would also solve some issues for Erik ten Hag, the new club manager. Last season, Ronaldo clashed with Harry Maguire regarding the teams captaincy. Ronaldo is also the highest-paid player in the Premier League and his exit from United should free up some space on Uniteds budget.
Ronaldo is due to return for the pre-season training this week. He is still expected to be in their pre-season tours of Australia and Thailand.