Maguire, who left Leicester for United for 80 million pounds, a world-record fee for a defender in 2019, was on the bench again in the 3-1 win over Arsenal on Sunday.
Maguire was a major doubt for the European Championship, but Gareth Southgate waited on him even though the former Leicester defender was not fit until the third group game.
Goals from Harry Maguire and Dele Alli and a string of fine second-half saves from goalkeeper Jordan Pickford were enough for England to progress to the last four.
England comfortably beat Sweden 2-0 on Saturday to reach the World Cup semi-finals for the first time in 28 years.
Maguire travelled with a group of friends and family to watch a 0-0 stalemate with Slovakia in St. Etienne in France two years ago when playing for Hull in the Championship.