49ers quarterback Trent Dilfer likely will miss Saturday's game against the Bengals due to a concussion. Dilfer suffered the injury in Sunday's loss to the Vikings. Coach Mike Nolan on Monday said he expects Dilfer to be listed as doubtful for the contest. Dilfer got hit in the head on a scramble attempt just before halftime and stayed down on the turf for a few moments before being helped off the field. Shaun Hill, who replaced Dilfer against the Vikings, is in line to start against the Bengals.