The march of players on offense to Halas Hall continued Wednesday with the Bears signing former San Francisco guard Chilo Rachal to a one-year contract.Rachal, 6-foot-5, 323 pounds, was a second-round pick for the 49ers out of USC in 2008, was a starter in 2009-10 before losing his No. 1 job. The signing was first reported by NFL Networks Ian Rappaport.The signing points in several possible directions for the Bears, who already have Lance Louis, Chris Spencer and Edwin Williams inside, and Chris Williams returning from a season-ending wrist injury. Rachals addition expands the option of Chris Williams returning to tackle, his more natural position and where the Bears are the thinnest on the offensive line.Rachal joins running back Michael Bush, quarterback Jason Campbell and wide receivers Brandon Marshall, Devin Thomas and Eric Weems on the list of additions to the offense, along with re-signings of tight end Kellen Davis and quarterback Josh McCown.That points to the Bears going stronger for defense in the draft.Rachals arrival injects serious competition with a guard group composed of players with histories at other positions. Spencer and Edwin Williams have been primarily centers, Chris Williams was a tackle and Lance Louis was a college tight end and tackle last year on an emergency basis.