Buffalo Bills Williams went undrafted in the
1997 NFL draft, and signed with the
Buffalo Bills as an
undrafted free agent the same year. He played in just one game his rookie season. During the 1998–2000 seasons, he was a regular contributor, but did not become a regular starter until the 2001 season. In 2000, he was named to USA Today's All-Joe Team, recognizing the NFL's most "overlooked, ignored and hard-working" players. During his final four seasons with the Bills (2001–2004), he started in all but four games. He became a free agent after the 2004 season.
Minnesota Vikings Prior to the 2005 season, Williams signed with the
Minnesota Vikings, the 1st signing for the team in 2005 free agency and a priority signing. Following an advice by then defensive coordinator
Mike Tomlin, Williams lost 15 pounds in the offseason. Williams played
nose tackle in the
Minnesota Vikings 4-3 defense, with teammate
Kevin Williams playing the Under Tackle position. They were known collectively as the "Williams Wall" as well as the "Williams Wrecking Crew" due to their physical presence at the line of scrimmage, an attribute that helped them lead the Vikings to the best rushing defense in the league for three consecutive seasons (2006–2008). As a player for the Vikings, he was selected to his first
Pro Bowl in 2006, and followed with consecutive selections in 2007 and 2008. He was also a second-team All-Pro selection in 2007. On December 2, 2008, Pat and teammate
Kevin Williams were suspended for 4 games by the league for violating its anti-doping policy, for use of a
diuretic, which can be used as a
masking agent for
steroid use. It is believed that the diuretic was found in a weight-loss supplement that he had been taking. In the 2009 season, Williams made 44 tackles, 2 sacks, and 2 forced fumbles. He announced that he might retire after the season, but decided to come back for one more year in 2010. He was the oldest defensive player in the NFL. On March 2, 2011, Williams announced that he would not re-sign with the Vikings for the 2011 season. "Everything’s good. I am not coming back. Going to go finish elsewhere." He ended his
NFL career playing
nose tackle when he retired. On April 23, 2013, Pat Williams signed a one-day contract so that he could retire as a Minnesota Viking. Pat Williams coaches at Wossman High School as a defensive line coach. Pat Williams helped create a Lineman Academy located at the
University of St. Thomas in
St. Paul, Minnesota. ==NFL statistics==