Thyrlos, DeVries may have been up before Walters, but the timing of when they pitched was off two days, I believe.
Anyway, I see DeVries as not 3 of x, but rather 2 of 3. That is, I think he, Walters, and eventually Manship or Swarzak (maybe interchangeable roles?) are vying for the last rotation spot at the end of the year.
Assuming a Pavano trade, keeping Liriano where he belongs, and Blackburn coming back, I see the August-September rotation, as preparation for 2013 as:
Hendriks
Bromberg
Diamond
Blackburn (unfortunately, a ballsy move would be to say "take your $5.5 million next year to the bullpen")
DeVries or Walters or Manship/Swarzak.
This sets them up for one FA signing at the top, and filler at the bottom in preparation for Gibson.
That's what I would do, anyway. What they will do . . .