First off, it's NOT just about him not staying healthy. It's due to him not being productive in a change of pace role. He looked like trash in Oakland behind Murray and looked mediocre behind Randle. It seems he needs a workload to really get going, and even then, he was incredibly inconsistent. As for his injuries, he's been injured for most of his career, and found a way to get injured off the field. He's one year older and he has a pile of injuries that will start to wear him down, he's also coming off a year where he had some heavy workload in games.
And yeah, it matters if he doesn't stay healthy and we lose a scat back that was leading our team in receiving through 3 weeks last year. I prefer to have diverse weapons on offense, have two good runners in Zeke and Morris and two good receivers Zeke and Dunbar. The battle should be between Morris, McFadden and Jackson. Dunbar is a completely different back, so unless we change up and have no use for Dunbar in the playbook we draw up this summer, I'd like to keep around the guy that was going off on teams before his injury.