Jennings, a second-round selection -- 62nd overall -- by the Indianapolis Colts in 2006, appeared in 53 games and started 21 in four seasons.
McKie, an undrafted free agent out of Temple, spent time with the Philadelphia Eagles and Dallas Cowboys before joining the Bears in 2003. He began his Bears career as a member of the practice squad before being elevated to the active roster on Nov. 21, 2003
"I just want to thank the Bears organization and the fans here in Chicago, it's been a great run," McKie told ESPNChicago.com. "I pretty much knew when Mike Martz was named offensive coordinator that there wasn't going to be a high priority placed on the fullback position.
"But I'm glad the Bears did this now, as opposed to after mini-camp or during training camp."
McKie's playing time dropped off significantly in 2009 as the offense placed a higher priority on the passing game after the arrival of quarterback Jay Cutler.
"I feel fresh," McKie joked. "I just hope I can land on my feet and help a team out this year. It's tough leaving all my teammates in Chicago, but everything happens for a reason."
Jeff Dickerson covers the Bears for ESPNChicago.com.