The 36-year-old had been training with the club in recent weeks and started their Cheshire Senior Cup win over Tranmere Rovers on Tuesday night. Simpson has been doing punditry for United&aposs in-house TV channel while he has also been back at Carrington observing and learning with the Academy staff as he studies for his coaching badges.
Macclesfield play in the Northern Premier League but are making waves in the non-league scene since a takeover fronted by Robbie Savage, himself a former United player. Alex Bruce, son of ex-United defender Steve, is in charge.
Simpson played 76 minutes of the 4-2 victory over Tranmere with former Everton star Oumar Niasse netting a hat-trick for the Silkmen. A crowd of 330 watched the tie.
Simpson could play for Macclesfield in their FA Trophy tie at Curzon Ashton this weekend. The full-back won the Premier League with Leicester City having come through the ranks at Old Trafford.