The Manchester United striker revealed that he plans to retire from Belgium duty following the continental competition in two years' time after helping his nation to third place in the World Cup earlier this year.
Southgate, however, has reassured supporters that the young attacker, who scored the only goal of the game as England beat Switzerland 1-0 on Tuesday, is rated by his club boss as much as anyone else.
The England manager hopes that the intensification of the domestic season, with some clubs competing on three fronts as Europe fully kicks in next week, will mean that they get opportunities.
However, he is now making it clear that the likes of Ruben Loftus-Cheek, with 33 minutes for Chelsea this season, and Fabian Delph, who has not featured at all for City, might have to be excluded if they do not start playing more regularly before the game in Rijeka on 12 October and, three days later, at the Estadio Benito Villamarín in Seville. So Phil came on at the end.
"He is a special talent", Southgate said.
A United source said: "Marcus loves the club and does not want to move but he wants to be a striker or at least play down the middle as a No 10".
'He is not going to give up trying to prove himself at United but he knows he may have a big decision to make soon'.
"It's not my business to interfere with club managers".
"He would have been a bit disappointed about the amount of time he had at the World Cup but it was important especially to get him in the penalty box and remembering the areas he needs to be scoring goals from".
"His confidence will be boosted I'm sure, with two goals against top-quality opposition". Possibly Everton is the sort of club you are looking at, just below the top six, for someone like Rashford, similar to what Lukaku did. "They have to rotate their squads".