The son of a professional boxer, Sexton was an expert coach. His side reached the FA Cup Final in 1979, but lost 2-3 against Arsenal, and were runners-up in the League to Liverpool in 1980. Under Sexton, Gary Bailey emerged from the ranks and Ray Wilkins arrived from Chelsea.

However, in 1980, injuries to the team began to cause poor results. Sexton became the first United manager to spend £1 million on a player, buying Garry Birtles from Nottingham Forest, but his own days were numbered.

United dispensed with his services on 30th April 1981, and he went on to manage Coventry City before joining the England coaching staff.