Yes they are going to need more starter depth, no doubt. Maeda could maybe provide that. Falvey said they would ramp him up as a starter, but did hint that by doing so you keep your options open.
I'm not sure either Gray or Ober have recent histories of arm trouble. For Gray it was hamstrings and Ober, his groin pull. But yes their disability is in question.
I would say outside of Maeda that Headrick would be the next man up. He looked good in his first taste of the bigs and is doing well. He just pitched 7 innings of 2 run ball, but only 4 strikeouts this time.