Montgomery is day-to-day with an unspecified injury and isn't likely to play in Saturday's preseason game against the Chiefs, Courtney Cronin of ESPN.com reports.
Montgomery's absence could free up more snaps for backup Khalil Herbert, who may or may not be headed for a larger role under a new coaching staff. Montgomery played 75 percent of snaps in his active games last year, but Herbert did solid work in relief when Monty missed time, running for 344 yards at a clip of 4.4 YPC in a four-game stretch Weeks 5-8. While his rookie year was otherwise quiet, Herbert at least did enough to have a safe lead over Darrynton Evans and Trestan Ebner for Chicago's No. 2 RB role. A shot at something more may depend on Montgomery's performance or health.