Manchester United's first pre-season fixture will be against Wigan Athletic on July 16.
Most of the first team are still away on holiday after respective Euro 2016 and Copa America campaigns.
This means Mourinho has turned to academy coach and former Manchester United player Nicky Butt to inform him who is ready to be promoted.
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In an exclusive interview with MUTV on Monday, he said: " I don't know them well but I just trust Nicky Butt, [head of football development] John Murtough and the [youth] structure's judgement, when they say we have a few players who, in a couple of years, can be first-team players.
"At Wigan, I will be bringing guys like Tyrell Warren and Axel Tuanzebe."
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So who do United have waiting in the wings of their world-famous academy system?
Last season, Nicky Butt heralded 17-year-old Tyrell Warren as "the best player on the pitch" during a UEFA Youth League match against Wolfsburg.
He defended really well, made some last-ditch challenges and did well against two men coming down the left-hand side for most of the time," Butt said.
The Manchester-born full-back made five appearances in the 2014/15 under-18 campaign before being promoted to Warren Joyce's under 21 side, who were crowned champions last season.
18-year-old Axel Tuanzebe was born in the Democratic Republic of Congo but grew up in Rochdale.
He captained the under-18 side in his first season and is credited as being a natural leader and having a strong personality on the club website.
Paul McGuiness, the coach who made him captain said, "It was the first time I'd picked a first-year scholar as captain."
"I don't think that has happened since Gary Neville was youth-team skipper. Axel did a very good job - on and off the field."
This young defensive duo sound very promising for United's future, but it remains to be seen whether Mourinho will attempt to bring them into the squad once the first team return to work.
But it won't only be the academy players who are desperate to impress the new first team manager.
With nine games to play before the transfer window closes, most of the first team will be anxious to prove their worth to their new manager, especially given the poor performances that dogged the first-eleven over the course of last season.