Pundit Stuart Pearce, says that the 20-year-old has potential to become world class but is not being utilised properly.
Rashford has struggled to hold down a first team place at Old Trafford in recent months, with Mourinho electing to rotate his front players.
And when he does start, the manager usually plays him out wide with Romelu Lukaku preferred in the middle.
Rashford did start in the 3-2 win over Newcastle on Saturday but was substituted on 67 minutes after failing to deliver.
The forward has still made 130 first-team appearances in his short United career but is becoming increasingly disillusioned at the club.
The youngster seems to come alive though when on England duty and after Southgate played him through the middle in their previous two matches, he scored twice.
England are currently preparing for Nations League clashes against Croatia on Friday and Spain on Monday.
And Pearce thinks Southgate has got to do what he can to maximise the player’s talent.
“Rashford is not getting enough club football,” Pearce said on The Debate on Sky Sports.
“He [Southgate] has got to create an international pathway to hopefully somewhere down the line get a player who has got a great deal of talent, flourish at international level.
“Gareth [Southgate] can’t dictate what happens at club level to Rashford, but he can when he has him in his care over the next 10 days.
“He’s got to give him as much minutes as possible with the hope that the end game in the next two to four years, we get a world-class striker out of him.”
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Mourinho, meanwhile, was rather critical when discussing Rashford’s performance against Newcastle.
He said: “Rashford was sad on the pitch, Scott [McTominay] was scared on the pitch.
“Maybe it was my wrong decision to play Marcus and Scott.
“They were not ready for this level of pressure that the man-hunting is bringing.
“The boys woke up on Saturday and they didn’t know if I was going to be at the game or not.
“For big boys like me it’s no problem. But for younger people I think ‘problem’ — and I think in the first half they clearly showed that.”