There has been much speculation about offensive linemen and the Bears. Mock drafters have prognosticated the Bears will draft offensive tackles, guards, middle linebackers and tight ends. There has been nary a word about cornerbacks. But cornerback is the Bears' hidden need for a number of reasons, but primarily because Charles Tillman, the team's most reliable corner, is 32. Tillman is an unusual athlete who goes to great lengths to preserve and prepare his body. But he already has performed at a high level longer than most corners, and the list of productive cornerbacks in their mid-30s in NFL history is a short one. Even if Tillman continues to produce, it might not be in Chicago. He is entering the final year of his contract. Tim Jennings is as well. Jennings, 29, could have a longer shelf life than Tillman. But he is coming off a career year, and it's fair to question if he ever will have another nine-interception season. Depth also is a concern. Kelvin Hayden became the nickel corner last year, but his contract is up. The Bears probably will try to re-sign him, but there are no guarantees they will. Also scheduled to be free agents are D.J. Moore and Zack Bowman. Given that Moore was benched last year and did not have a very good season, it seems unlikely he will be back. The previous coaching staff looked at Bowman primarily as a special teams player, and defensive backs coach Jon Hoke is one of the holdovers from the old staff. That makes it seem likely that if Bowman returns it will be in a similar role. Cornerback was enough of a concern last April that the Bears used two draft picks on corners, choosing Isaiah Frey in the sixth round and Greg McCoy in the seventh, but neither had an impact. - See more at:,0,5492222.column#sthash.SflHz6yE.dpuf