The young midfielder, Mather, has recently inked a new, undisclosed long-term contract with the club. The deal comes as Mather's previous contract, set to expire in 2025, was nearing its end.
Reports suggest the new deal runs to 2027 with an option for another year.
The 19 year-old is an FA Youth Cup winner and spent time on-loan with Rochdale last season.
Mather was also part of United's tour of the US this past preseason.