Spurs' head of coaching and player development, McDermott rejected an approach to join United, preferring to stay at White Hart Lane to continue working alongside manager Mauricio Pochettino, per the Times' James Ducker.
The report indicated that United approached McDermott before Christmas having "earmarked him for a key role in revamping their youth setup."
The Spurs man's reputation has been enhanced by his development of players like Harry Kane, Tom Carroll, Danny Rose and Ryan Mason, but he was clearly not open to a move to Old Trafford.
Per Ducker, United are preparing to make wholesale changes to their academy having admitted it needs to be improved.
Once a breeding ground for some of the best young players in the world—see the likes of Paul Scholes, Ryan Giggs and David Beckham—few academy graduates from United have made the grade in recent years.
Tom Cleverley and Danny Welbeck promised much but have since moved on to other clubs, while Adnan Januzaj and James Wilson have failed to progress after showing early potential in recent years.
Louis van Gaal put faith in the likes of Paddy McNair and Tyler Blackett when he first arrived at the club, but they have not been able to nail down regular places in the squad under the Dutchman—indeed Blackett is currently on loan at Celtic.
Spurs are undoubtedly producing better young players from their academy than United, with Rose, Mason and Carroll all regulars in Pochettino's squad and Kane one of the best strikers in the Premier League at just 22 years old.
United were clearly hoping for McDermott to produce similar results in Manchester, but they will now have to look elsewhere as they aim to improve their academy.