In recent weeks, Ronaldo, who left United in 2009 for the Bernabeu after six years at the club, has been linked with a possible return to the Red Devils due to his uncertainty with the Spanish giants.
Following the speculation, it has since emerged that Rooney could be shown the door by manager Sir Alex Ferguson in the summer after he was dropped to the bench for United's 2-1 defeat to Madrid in the Champions League on Tuesday.
It is understood Rooney's advisers feel that the 27-year-old will move on at the end of the season in order for United to bring in Ronaldo or another high-profile signing, according to the Daily Star.
"Wayne wants to play every game, let alone the most important one of all," the newspaper quotes a source as saying. "He can't hide from the feeling this is the beginning of the end at United."
Reports have claimed that Ferguson has grown concerned over the England international's lifestyle off the pitch.