With David Robertson coming off the DL on Friday, the Yankees have optioned David Phelps to Single-A Tampa. The reason they have done this is so he can build up his arm strength at a lower level before going to Triple-A to start. In theory, once he builds up his arm strength, he will be the starter-in-waiting once the Yankees have an injury to their rotation.
Freddy Garcia, the de facto long man, probably is teetering on the territory where he won't be a viable option if a starter is needed. (Before you yell at your screen, I realize he hasn't really gotten anyone out this year, which hurts his starting candidacy.)
The Yankees could have released Garcia and eaten the rest of his $4 million salary, but chose not to do that. At least, not yet.
Phelps went 1-2 with a 2.94 ERA.