The Atlanta Falcons replaced Michael Turner with another proven, productive running back.

Steven Jackson, the top running back in free agency, agreed to a three-year, $12 million deal with the Falcons on Thursday.

Also getting new deals were backup quarterback Matt Cassel in Minnesota, pass rusher Cliff Avril in Seattle and cornerback Keenan Lewis in New Orleans. The New York Giants signed defensive backs Ryan Mundy and Aaron Ross.

Day 3 of the NFL's free agency frenzy was highlighted by the 29-year-old Jackson moving on from St. Louis after his eighth straight 1,000-yard season.

"I think this is a very big signing for us," Falcons general manager Thomas Dimitroff told The Associated Press. "It continues to bolster our offensive firepower."

Jackson would have earned $7 million with the Rams in 2013 before he opted out of his contract to become a free agent. His 10,135 yards rushing for his career are the most of any active player.

The Falcons released Turner, defensive end John Abraham and cornerback Dunta Robinson on March 1. Turner had 800 yards rushing last season, his low total in his five seasons in Atlanta.

Jackson averaged 4.1 yards per carry with the Rams and gives Falcons quarterback Matt Ryan another receiver. Jackson had at least 38 catches in each of his last eight seasons in St. Louis.

The Patriots moved quickly to replace Wes Welker, who signed with Denver on Wednesday. New England lured former Rams receiver Danny Amendola on a deal that would reportedly pay him $31 million over five years.

Also Thursday, the Patriots announced the signing of running back Leon Washington, who has played seven seasons with the New York Jets and Seattle Seahawks.

The Vikings grabbed Cassel shortly after the Kansas City Chiefs let him go, a person with knowledge of the deal told the AP on condition of anonymity because it had not been officially announced.

Also Thursday:

  • The Eagles began revamping their secondary by signing cornerback Cary Williams and safety Kenny Phillips, giving them four new faces in the defensive backfield in a three-day span. They also signed linebacker Connor Barwin to a six-year deal.

  • The Tampa Bay Buccaneers signed linebacker Jonathan Casillas and receiver Kevin Ogletree.

  • The Chiefs agreed to terms with cornerback Sean Smith on a three-year deal.

    Lions: Offensive lineman Jeff Backus announced his retirement after 12 seasons with Detroit.

    Tuck rule: The tuck rule could disappear from NFL games if owners approve a proposal from the competition committee to dump it.

    The rule was among the NFL's most obscure until it became infamous during the 2001 playoffs in New England, when Tom Brady apparently lost a fumble late in a game against the Raiders. Initially ruled a fumble, it was reversed under the tuck rule, the Patriots kept the ball and eventually beat the Raiders.