The 18-year-old missed the start of the 2023-24 campaign due to an ankle injury which he picked up during the team's preparations for the current season.
Mainoo has been a vital player for the Red Devils since the middle of December, though, starting each of their last 12 Premier League matches.
The midfielder penned a new deal at Old Trafford last January, with his current terms due to run until the end of the 2026-27 campaign, with the option of a further 12 months.
However, there have been claims that Mainoo is set to be rewarded for his development this season, with the youngster in line for a substantial wage rise.
According to Football Insider, 'advanced talks' are currently taking place, with all parties confident that an agreement will be reached over a new contract at Old Trafford.
The report claims that it will be a 'mega-money new agreement' for Mainoo, with the teenager set to have his weekly wage packet increased to reflect his importance to the team.
Mainoo starred for Man United in their 4-3 win over Liverpool in the FA Cup last weekend, and it is believed that his performance in that contest led to England manager Gareth Southgate handing him a senior call-up.
The youngster was originally named in the England Under-21s squad, but it was announced earlier this week that Southgate had called him into the senior squad for the upcoming friendlies with Brazil and Belgium.
Mainoo is therefore seemingly firmly in Southgate's plans when it comes to Euro 2024, with a strong end to the season likely to earn him a spot in the Three Lions squad for the summer
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