The 19-year-old left-back has joined Unique Sports Group after moving to M+C Saatchi Football in September, in another indication that he is becoming increasingly concerned about his lack of first-team opportunities at Old Trafford.
Amass is understood to fear that his development is stagnating after enjoying regular football during loan spells in the Championship last season. He initially joined Sheffield Wednesday before switching to Norwich City in January, but a hamstring injury brought his campaign with the latter club to an early end.
Manchester United decided to retain him as cover at left-back after missing out on Lewis Hall, but he has struggled to make an impression under manager Michael Carrick.
Despite Luke Shaw missing eight of United's 13 matches this season through two separate injuries, Amass has not started a game. Carrick has instead used Diogo Dalot, Noussair Mazraoui and even centre-back Ayden Heaven in the position.
Amass has made only two substitute appearances, the most recent coming during the 4-0 Champions League defeat against Como. He was subsequently left out of the Premier League squads for defeats against Bournemouth and Chelsea, despite Shaw's continued absence.
The lack of involvement represents a frustrating setback for a player who had been given opportunities to impress during United's pre-season preparations before making his senior debut in March 2025 under Ruben Amorim.
His previous representative, Jason Mac, had helped arrange the loan moves to Sheffield Wednesday and Norwich. However, the teenager's latest change of agency suggests that securing a clearer route into senior football has become a priority.
United signed Amass from Watford's academy in 2023, and he was first included in a senior matchday squad against Liverpool in April 2024. He remains under contract until the summer, although the club hold an option to extend the agreement by another year.
A January departure would give Amass the opportunity to find regular minutes elsewhere, having seen his progress stall at a time when United have continued to use alternative options at left-back.