After an outstanding performance during the Senior Bowl, Williams went from a marginal first round choice to a possible top 12 pick for the 2003 NFL draft in most scouts' estimation.

Williams was named NFC Defensive Rookie of the Month when he had 18 tackles, 5.0 sacks, a forced fumble and an interception in the 4-game stretch and joined Carl Eller (1964) and Al Noga (1988) as the only rookie defensive ends in team history to start the season opener when he debuted in the lineup at Green Bay September 7 and also joined defensive end Lance Johnstone as players with 10.0+ sacks, the first time in Vikings history since 1993 when Chris Doleman and John Randle accomplished the feat.

In 2007, during the NFL Kickoff game, Williams intercepted Atlanta Falcons quarterback Joey Harrington and ran 54 yards for a touchdown in the 1st quarter.

In week 14 of the same season, Williams intercepted San Francisco 49ers quarterback Trent Dilfer and returned the pick for a touchdown in the 1st quarter.

The case review had been ongoing through the entire 2009 and 2010 NFL seasons, but in 2011, he was suspended for only 2 games under the rules of the new Collective Bargaining Agreement.

On July 27, 2016, Williams signed a one-day contract with the Minnesota Vikings before announcing his retirement from professional football.

Williams married in June 2005 to Tasha, who ended her collegiate basketball career in 2006 as a senior at Louisiana Tech and helped the Lady Techsters to the NCAA Tournament, earning all-conference honors.