Despite Ronaldo's frustration at starting just two games this season, the five-time Ballon d'Or winner has become one of Rashford's biggest cheerleaders.
A source told The Sun: “Ronaldo has been a bit of a pain in the dressing room and some of the players have been frustrated about the fact he missed pre-season and has been sulking around Carrington.
“But since the transfer window closed, his attitude has improved and he has been very helpful with Marcus.
“He's been spending time with him, talking about the game and giving his constructive criticism about positioning on the pitch.
“Marcus has been a bit surprised by it because it's always difficult when you're playing and a team-mate isn't and you're both fighting for the same position.
“But the relationship between the pair has never been better and Marcus knows he can learn a lot from him.
“He's grateful for the advice and for the fact that Ronaldo seems genuine in that he wants Marcus to improve and succeed."