He played in Major League Baseball (MLB) for the San Francisco Giants, Chicago Cubs, Washington Nationals, Los Angeles Angels of Anaheim, Houston Astros, Texas Rangers, Philadelphia Phillies and St. Louis Cardinals, and in the Chinese Professional Baseball League (CPBL) for the Uni-President Lions.

In April 2008, he signed a contract with the Long Beach Armada of the Golden Baseball League.

On June 24, 2008, the Los Angeles Dodgers purchased his contract and he played in their minor league system through the end of the season.

At the end of the minor league season, September 5, 2008, Williams was waived by the Dodgers and then claimed by the Oakland Athletics.

[3] Williams did not play for Oakland and was not tendered a contract after the season, making him a free agent.

He subsequently re-signed with Oakland and spent 2009 with their top farm club, the Sacramento River Cats of the Pacific Coast League.

Williams played winter baseball for the Indios de Mayaguez in Puerto Rico in 2008–09.

In June 2012, Williams had breathing problems and later collapsed in the clubhouse, forcing the Angels to place him on the disabled list.

[15] On March 7, 2023, Williams was announced as the pitching coach for the State College Spikes, member of the MLB Draft League.

[16] On January 23, 2024, Williams was named the pitching coach for the Yolo High Wheelers of the Pioneer League for their inaugural season.

[19] He was well known for wearing a puka shell necklace at all times on the playing field, in honor of his mother Deborah, who died of breast cancer in 2001 while he was still a minor league pitcher.

He also sported a pink glove whenever he pitched, a symbol for the efforts of finding the cure for breast cancer.