Ronaldo will miss Saturday's Premier League game against Chelsea at Stamford Bridge after being dropped by manager Erik ten Hag as punishment for refusing to play as a substitute in Wednesday's 2-0 win against Tottenham at Old Trafford.
The former Real Madrid and Juventus forward also angered Ten Hag by leaving the substitutes' bench before the end of the game to walk to the dressing room and leave the stadium without the manager's permission.
Having been criticised by Ten Hag in July for going home during the preseason friendly against Rayo Vallecano at Old Trafford, Ronaldo's latest display of indiscipline has increased the prospect of the Portugal international leaving United in January.
But sources have told ESPN that the United hierarchy, led by American owners the Glazer family, have been willing to offload Ronaldo since he made it clear in the summer that he wanted to leave the club.
Sources have said that United, who signed Ronaldo in a €15 million deal from Juventus in August 2021, have not sought a fee for the player in the hope that another club would be prepared to take on his £500,000-a-week contract.
But aside from interest from Saudi Arabian team Al Hilal, United have had no enquiries about Ronaldo, with even ambitious and well-funded teams in Turkey proving to be unmoved by the prospect of signing a player who took his club goal tally to 700 with his strike against Everton earlier this month.
Sources have said that there is a hope within Old Trafford that clubs could emerge as potential options for Ronaldo if he enjoys a productive World Cup with Portugal in Qatar next month. And with six months remaining on his United contract, there is also the possibility of Ronaldo being loaned out in January should another club be willing to agree a deal to pay a proportion of his wages.
But with his 38th birthday approaching in February and just two goals in all competitions for United this season, Ronaldo is struggling to attract interest from clubs who could offer him an escape route from Old Trafford in January.