LAKE FOREST – Chicago Bears running back Marion Barber said he plans to retire.

His decision, posted on the team's Web site Friday, comes one day after Michael Bush signed a four-year, $14 million contract to be part of a backfield that includes disgruntled Pro Bowl running back Matt Forte.

The 28-year-old Barber spent his first six NFL seasons with the Dallas Cowboys before signing with the Bears in 2011. He was a backup to Forte last season and then saw extensive duty when Forte sprained his knee in early December.

Barber had six touchdowns and 422 yards rushing last season, but will be remembered for two gaffes in a costly loss at Denver when he ran out of bounds as the Bears were trying to kill the clock, and then fumbled in overtime.

A fourth round pick of the Cowboys in 2005 out of Minnesota, the hard-running Barber gained 4,780 yards rushing on 1,156 carries with 53 touchdowns in his career. He also caught 179 passes for 1,330 yards and six touchdowns.

Barber, who had little to say to reporters during his only year in Chicago, told Larry Mayer of ChicagoBears.com:  "I want to thank everyone who gave me the opportunity to play, and I'm very thankful to have had the chance to suit up for two of the NFL's most storied organizations."

"I want to thank everyone who helped me become a better player," Barber said. "I owe a lot to a lot of coaches, and am also very grateful to the owners and organizations I played for. Last but not least, I want to thank the fans for the support and inspiration they gave me."

Forte, who has not been able to reach a long-term contract deal and was given the franchise tag, was not happy when the Bears signed Bush.

On his twitter account he said he had been disrespected after doing everything he'd been asked to do by the team. He later tweeted that he was not upset at the Bears signing another running back, adding that "undervaluing a player under his market value is another story!"