"It's not my business to interfere with club managers, they have a hard job to do and they have big squads at the top six, huge competition for places, so Jose thinks the world of Marcus", Southgate said.
He now returns to Old Trafford to begin a three-game suspension for a red card picked up 10 minutes after going on as a sub in their win at Burnley in the last game before this worldwide break.
Romelu Lukaku has been United's undisputed first-choice striker since arriving in a £75 million deal from Everton in the summer of 2017, leaving Rashford to get the majority of his first-team minutes from the substitutes' bench or starting on the wing.
"I can expect that Sunday some of them will wake up in the morning and as always the first thing they think is Jose Mourinho".
"Probably you should remind them he is suspended and can not play".
'Performances with England, of course I'm happy, he played well, competed well, he score and especially in a period where he comes with some sadness after his suspension and it was very good that he did that.
"He (Rashford) has still played a lot of football, although maybe not the continuous starts, and I'm really pleased for him that he leaves England full of confidence".
"Right now I am at Chelsea and my focus is at Chelsea and learning at Chelsea", said Loftus-Cheek.
A move to another club could provide more playing time but sticking at United will help him win silverware.
Everton have been tipped as one of the sides Rashford could join, if he does leave United.
"I'm not sure when I am going to play".
Mourinho has been under criticism since the start of the new season as United lost two of their first three Premier League matches.
"A prodigious talent", former England striker Gary Lineker tweeted after Rashford scored England's goal with a cushioned volley in the 1-0 win over Switzerland in a friendly on Tuesday. He returned to Carrington on Monday but Mourinho admits the 23-year-old is a doubt to face Watford, who have started the season with 12 points from four games.
Marouane Fellaini is a doubt for the Watford game, with Mourinho also suggesting Ander Herrera may be ruled out because of an ankle problem.
"I don't know [if he will play]", said Mourinho.
The Premier League legends claimed his development under Mourinho will be stifled due to the lack of game time afforded to him in his favoured central striking role.