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.

And the Houston Texans were rolling out the red carpet to make their pitch to safety Ed Reed.

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. It gives us not only strength, power in running ability but also the versatility to catch out of the backfield, which is a very important part of this offense."

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.

"We're hoping he has his best years ahead of him, there's no question about that," Dimitroff said. "We think he still has much fuel in the tank and I know that he believes that."

The Broncos have gone on a spending spree for the second straight spring and on Thursday, Wes Welker, among the top prizes in this year's free agent class, was welcomed to town. He said that while he was sad to leave Tom Brady in New England, he was thrilled to join Peyton Manning in Denver.

The most productive receiver in the league over the past six seasons, Welker said he's also eager to team up with young 1,000-yard receivers Demaryius Thomas and Eric Decker to give the Broncos the "Three Amigos" Version 2.0.

"I think they were another big part of me wanting to come here," Welker said. "They did a great job last year and hopefully I can just come in and try to help out."

Welker signed a two-year, $12 million deal in Denver after spurning the Patriots' offer of $10 million over two years.

Also introduced at the Broncos headquarters Thursday was right guard Louis Vasquez, who signed a four-year, $23.5 million contract, the largest of Denver's seven signings so far, a number that's surprised some seeing as how they went 13-3 last season.

"We accomplished a lot, and we're trying to accomplish more," Broncos coach John Fox said.

And anyone who thought Broncos quarterback-turned-boss John Elway would stand pat after a 13-3 season: "They don't know John Elway," said former Bronco safety John Lynch.

"I love it," Lynch said. "They're in it to win it. I think they're doing it prudently, too. Welker was a bargain."

Fox cautioned that it's still mid-March and while some dollars are guaranteed, results aren't.

"These things aren't won on paper, and right now, we're on paper," Fox said. "That game is won between the lines, and anybody will tell you, we've got a lot of work (ahead)."

The Patriots moved quickly to replace Welker, luring 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.

Amendola, 27, is a 5-foot-11, 188-pound former rookie free agent from Texas Tech - the same school as Welker.

A five-time Pro Bowler, Welker averaged 112 catches and six touchdowns a year over six seasons with the Patriots. Amendola has struggled to stay healthy, playing in 16 games only once.

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.

It was a busy day for the Vikings, who also were hosting Green Bay Packers free agent receiver Greg Jennings for a visit.

Cassel spent the past four years in Kansas City, making the Pro Bowl in 2010 after throwing for 27 touchdowns and just seven interceptions. But he has struggled the past two years, with 16 TDs and 21 interceptions. He'll replace Joe Webb as Christian Ponder's backup.

In Houston, Reed was picked up by general manager Rick Smith in the private jet of Texans owner Bob McNair.

The move was tweeted by the team and then Texans defensive coordinator Wade Phillips tweeted that he was meeting with the Ravens veteran in his office, too.

Signing Reed would make up for an otherwise disappointing week for Houston. The Texans cut receiver Kevin Walter, then lost tight end James Casey to Philadelphia and safety Glover Quin to Detroit after the opening of the free agency signing period.

The 34-year-old Reed played for the Super Bowl-winning Baltimore Ravens. A nine-time Pro Bowler, Reed is the Ravens' franchise leader in interceptions with 61.

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.

• Detroit's durable offensive lineman, Jeff Backus, announced his retirement after 12 seasons with the Lions.