Sillett helped Coventry to win the Third Division title in 1963–64, but his playing days were limited after suffering a back problem.
[13] When Mackay departed in 1986 with just three games of the season left, Sillett was appointed chief coach alongside George Curtis.
[16] Sillett became Coventry's sole manager from the 1987–88 season onwards,[17] while Curtis returned to working on matters not related to the day-to-day running of the team.
[21] The 1987–88 season began with another trip to Wembley, as Coventry played league-champions Everton in the FA Charity Shield.
[19] The first league game was a repeat of the FA Cup final, as Coventry played Tottenham, Speedie scoring in a 2–1 win.
[22][23] The season was a disappointment, however, with their defence of the FA Cup ending in a fourth-round home defeat to Watford and another tenth-place league finish.
[24] The following season City suffered one of the biggest upsets in FA Cup history, as they lost 2–1 to non-league Sutton United in the third round.
[24] Coventry replaced a number of players during the 1989 close-season, buying defender Peter Billing and acquiring Liverpool's Kevin MacDonald on a free transfer, with David Phillips and Steve Sedgley leaving the club.
The season started slowly, however, and Sillett was sacked by Chairman John Poynton, and replaced by Terry Butcher, who arrived from Rangers as player-manager, for a £400,000 fee.