In June 1991, he was appointed by Alex Ferguson as the manager of Manchester United's reserve team, a position he held for ten years.

A month later, he signed his first professional contract, but it was not until May 1966 that he made his first-team debut, playing on the right wing in the final four league games of the 1965–66 season.

After living in the United States for eight years, Ryan returned to England to take over as manager of the Luton Town reserve team.

Following Luton's dismissal of Ray Harford, Ryan was promoted for an 16-month spell as manager on 11 January 1990, saving the club from relegation on the last day of two successive seasons.

After assistant manager Brian Kidd left to manage Blackburn Rovers in December 1998, Ryan stood in as Ferguson's assistant until Steve McClaren's appointment in February 1999, taking full charge of the side for their 3–2 defeat at home to Middlesbrough on 19 December 1998, which Ferguson missed in order to attend a funeral.