LAKE FOREST, Ill. -- Lorenzo Booker's prospects of being available to play against the Indianapolis Colts are slim after the running back missed his fourth consecutive practice on Friday. The Bears likely will be forced to make a personnel change to cover Booker's assignments on special teams.

Booker, a five-year NFL veteran, made the Bears' 53-man roster as the No. 3 tailback despite sustaining a head injury in the club's final preseason game last week in Cleveland. He is officially listed as questionable for Sunday.

"It would be a loss (to not have Booker available) but we have (depth) at those positions. You try to have a few players that can do some of the same things," Bears coach Lovie Smith said. "We feel we have a couple of guys that can do some of the same things."

Included in that group is practice squad running back Armando Allen, who has experience playing the important role of the personal protect on the punt team, a spot the Bears expected Booker to occupy in the regular season.

Allen spent 12 weeks on the Bears' practice squad last season before being elevated to the active roster for the final two games of the regular season when he carried the ball 15 times for 48 yards. He had a strong preseason but lost out to Booker, who the coaches believed offered a little more versatility on special teams.

If they promote Allen from the practice squad, the Bears would need to make a corresponding roster move to get the roster down to 53.