Known for his diminutive height and his dogged tackling, Williams spent the vast majority of his playing career in the United States, playing one season in the National Professional Soccer League, two in USISL, two in the USL A-League, and eight in Major League Soccer, most notably for D.C. United.

[1] Williams' career has been closely tied to Bruce Arena, former coach of the United States men's national team.

Making up for his height with his ferocious shadowing of the opponent's top playmaker, he became an integral member of the early DC teams, helping them to three MLS Cup titles.

His MLS career ended with the Metros in a trade with Eddie Pope and Jaime Moreno for Mike Petke, a draft pick, and an allocation before the 2003 season.

[6] In January 2019, Williams was hired as the head coach of Loudoun United FC in the USL Championship.

[8] In August 2020 during the “MLS is Back Tournament” in a COVID-shortened season, Williams assumed head coaching duties of the New England Revolution for three games (a win and a tie, extending the team's unbeaten streak to eight games) while Bruce Arena served a temporary suspension.

On August 1, 2023, the New England Revolution announced that Bruce Arena was placed on administrative leave amid allegations of "insensitive and inappropriate remarks[9]"and that Williams would act as interim head coach pending a related league investigation.