It's neither factual that the past performance of each is "luck," nor that the past isn't predictive. Those are called assertions, or theories, not facts. Luck MIGHT be a factor. I'd buy PROBABLY is a factor. IS the only factor? No. This is baseball. Neither you, I, or the folks at Fangraphs have completely figured out why things happen. And we sure as heck can't say for a fact what is, and isn't going to happen in the future. Past performance is what everyone uses tp predict the future...including you. You're just assigning different values to different parts of past performance. I think May should stay in the rotation, probably ahead of Pelfrey. But it's absolutely a close call at this point, and there are reasonable arguments for any of the three. That's the "facts," as I see them.