[4] He turned professional in 1975 and made his debut aged 17 on 6 April 1976, in a 1–0 victory away to local rivals, Portsmouth in a game where Peter Osgood was dropped for disciplinary reasons.
[10][11] He succeeded Alan Ball as team captain and led The Saints to an FA Cup semi-final and to runners-up position in the 1983–84 First Division.
[12] The following season, manager Lawrie McMenemy was becoming disillusioned with Southampton, feeling that he had taken the club as far as he could and this disillusionment spread to several senior players including Williams, leading to a transfer request.
[3][9][13] After making his debut in a North London derby match against Tottenham Hotspur on 1 January 1985, Williams was a regular for the remainder of the season.
[3][14] By the time he had recovered, George Graham had taken over as Arsenal manager, and initially Williams thrived, playing on the right hand side of midfield, alongside a young David Rocastle.
[20][7][3] His eventually retired in 1993, after a brief playing spell at Derry City where he made his League of Ireland debut against Shamrock Rovers in October 1993.