Le'Veon Bell is going to start, but the Steelers did not sign LeGarrette Blount to primarily provide injury insurance. Coach Mike Tomlin has made it clear that both Bell and Blount will figure prominently in the running game. The Steelers are serious about running the ball early and often this season, but Bell will have carries siphoned away from him because of Blount's ability to wear down defenses.
Bell's value in 2013 hinged on his huge workload (22.2 touches per game, #3 in the league), so if carries are indeed 'siphoned away,' he's not likely to put up low-end RB1 numbers in 2014. Blount is available very late in drafts and was impressive for the Patriots last season. If Bell were to get injured, Blount would hold RB2/RB3 value as the main runner for the Steelers.