A) Greinke came to ML as a starter, looked OK then struggled a bit (according to his ERA, anyway).
B) Next, he spent some time starting in AA, then came back to ML as a reliever for a 3 appearances. The next season he was considered a starter, then was moved to the pen.
C) At the end of that season, he was put back in the starting role, and it stayed that way.
A) Crow came to AA as a starter, then was promoted to ML the next season as a reliever.
B) He pitched well enough that they decided he was now and forever a reliever.
C) He was never given the opportunity to finish his potential development into a starter.