Running back Ricky Williams has informed Baltimore Ravens officials he is retiring, according to a league source.
The team later confirmed Williams' decision with a press release and announcement on its official site.
He completes a distinguished career and was a very effective change-of-pace power runner for Baltimore in 2011.
Williams, one of the NFL's oldest running backs at 34, had career lows in carries (108) and rushing yards (444) after joining the Ravens last summer on a two-year contract, but he filled a critical backup role to Ray Rice. Williams finished his career with 2,431 carries for 10,009 yards and 66 touchdowns after playing for the Ravens, Dolphins and Saints over 11 seasons in which he posted five 1,000-yard seasons.
He was suspended for the entire 2006 season for his fourth failure of the league's substance abuse policy, spending the year playing for the Toronto Argonauts of the Canadian Football League. He retired previously before the 2004 season when facing a four-game suspension for violating the league's drug policy. He returned in 2005.
"Thank you all, but this ain't it, I'm gonna do something really special. 'Be you and change the world,' " Williams tweeted Tuesday.
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"The NFL has been an amazing page in this chapter of my life," Williams said later in the release. "I pray that all successive adventures offer me the same potential for growth, success and most importantly, fun. I want to thank all my fans, teammates, coaches and supporters for the strength they've given me to overcome so much."
Rice called Williams, who retires as one of just 26 players to top 10,000 career rushing yards, a Hall-of-Famer.
"I was a big fan of Ricky before we were teammates, but being around him this year is the best thing that happened to me in my NFL career," Rice said. "As a young player, you need to be around a guy who knows what he is doing, and Ricky was tremendous to learn from.
After winning the Heisman Trophy with Texas, Williams broke into the NFL in 1999 with the New Orleans Saints, who took him fifth overall. The Saints traded eight draft picks to the Washington Redskins in order to move up and select Williams in that draft. The Saints sent each of their six picks in the 1999 draft, as well as first- and third-round picks in the 2000 draft, to the Redskins. After four seasons with the Saints, Williams was dealt to Miami in exchange for first- and fourth-round picks in the 2002 draft, as well as a conditional pick that ended up as a first-rounder when Williams ran for more than 1,500 yards in his first season with the Dolphins. Williams led the NFL in 2002 with 1,853 yards rushing with the Dolphins and made the Pro Bowl that season.
A team source said they would gladly have welcomed back Williams, who just last week said he was in good shape and was excited for next season.
"My body feels good and I know I'm going to train hard and so I'm excited about next year," Williams told the team's official site last week.
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The Associated Press contributed to this report.