History of Manchester United F.C. (1969–1986)

Following an eighth-place finish in the 1969–70 season and a poor start to the 1970–71 season, Wilf McGuinness was sacked as manager of Manchester United in December 1970 after just 18 months in charge. Matt Busby returned to the manager's position on a temporary basis, and McGuinness returned to his position as reserve team coach.

Source: Wikipedia — History of Manchester United F.C. (1969–1986) (CC BY-SA 4.0)