I think that the most interesting and somewhat wide open battle of the spring is the competition for the starting rotation. Scott Feldman clearly has a spot lined up, but after him, the picture is not so clear, so I think the ST results matter more than they usually would, for everyone except Feldman.
Dallas Keuchel has clearly produced the best results so far, and the reports on his stuff have been very enouraging as well.
Jerome Williams has been the next most impressive so far, followed closely by Cosart and Harrell.
Peacock and Oberholtzer have been awful, though Peacock has only pitched one inning so far (it was a doozy).
Prior to ST, I thought the favorites for the rotation, following Feldman, were Cosart, Oberholtzer, Peacock, and Keuchel, in that order, followed by Williams then Harrell. But even after a small sample, I think the picture has changed.
For me, Cosart still looks like the best bet, followed by Keuchel. I always thought Peacock was the most vulnerable rotation candidate, and after only one bad inning, he's got to be on the outside looking in right now. Oberholtzer was pretty good last year, so I think he's going to get a pass unless the bad pitching continues. So which of Williams or Harrell has the edge right now? Personally, I think the news surrounding his signing, along with the slightly superior ST performance gives him the current edge over Harrell right now.