The Atlanta Falcons found their replacement for Michael Turner on Thursday by agreeing to terms with Steven Jackson, considered the top free-agent running back, on a three-year, $12 million deal.The 29-year-old Jackson had 1,042 yards rushing and four touchdowns with the Rams last season. It was his eighth straight season with more than 1,000 yards rushing."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."In separate posts on his Twitter feed, Jackson referred to Dimitroff and Falcons owner Arthur Blank as he thanked the Falcons for the new deal."To the AMAZING Atlanta Falcons Owner, GM & Management team, I SINCERELY THANK EACH OF YOU for making this happen. I EAGERLY anticipate 2013!" Jackson tweeted.Jackson would have earned $7 million with the Rams in 2013 before he opted out of his contract to become a free agent.He tweeted his thanks to the Rams "for believing in me & allowing me to be an integral part of this team for so many years."Jackson's 10,135 yards rushing for his career are the most of any active player. He set career highs with 1,528 yards rushing and 13 touchdowns with St. Louis in 2006.Turner's average of only 3.6 yards per carry last season set a career low. The Falcons released Turner, defensive end John Abraham and cornerback Dunta Robinson on March 1. He had 800 yards rushing, 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 to target. 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."Turner's modest total of 19 catches last season set a career high. He had his first career touchdown catch.The deal with Jackson came only two days after the Falcons announced tight end Tony Gonzalez is returning for the 2013 season after saying last year he was 95 percent sure he would retire.The Falcons also have re-signed strong safety William Moore and right guard Garrett Reynolds.