"Ivory had [a rib injury] and did not finish" Ryan told reporters after the game. "He should be fine."
The protocol that NFL teams follow with rib injuries is to get players X-rays as soon as possible. By Rex Ryan saying that Ivory should be fine could indicate that the X-rays were negative for a fracture and might just be soft tissue damage. We expected that even if the injury was minor (which it seems like it was) the Jets pulling Ivory from the game had more to do with precautions since this is preseason football and not a game that "counts" when it comes to divsional standings or a playoff berth.
While the Jets depth at running back might be one of the best in the league, the whole group is very interdependent in each other for specific roles. Johnson is tabbed as the team's best pass catcher and dynamic perimeter playmaker. Ivory is lined up to do the heavy lifting betwen the tackles. Bilal Powell is the best blend of both and can fill in should either need to sit. But with Powell sitting last night due to a hamstring injury of his own, the injury to Ivory seemed to cause concern about the whole group.