The 18-year-old has been a shining light in a troubled campaign for Erik ten Hag's side and is now a weekly starter for the Red Devils, making 19 first-team appearances in the current campaign.
Mainoo has scored twice in that run, netting against Newport County in the FA Cup and against Wolverhampton Wanderers in the Premier League, and he has caught the eye with his tenacious displays in the middle of the park.
The 2005-born lynchpin has made the starting lineup for each of Man United's last 12 top-flight contests, and he is expected to be rewarded with a bumper new contract thanks to his breakthrough campaign.
Mainoo has represented England at Under-17, Under-18 and Under-19 level, only making his debut for the latter team last year, but he has inevitably been tipped to force his way into Southgate's thinking ahead of Euro 2024.
With Mainoo also eligible to play for Ghana, it was reported last month that England had planned to fast-track him into the senior squad and would consider calling him up to their next squad, but the midfielder wanted to keep his options open.
Southgate will reveal his selection for England's upcoming friendlies with Brazil and Belgium on Thursday, but according to Sky Sports News reporter Rob Dorsett, a call-up for Mainoo is considered unlikely.
Instead, the 18-year-old is expected to be included in Lee Carsley's Under-21s squad for the first time, and he could still be promoted to the senior squad if injuries force withdrawals.
Dorsett adds that Mainoo is viewed as a «key prospect» by the FA, who still plan to accelerate his
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