I really hate this argument. Look, if you want to put May out there....fine, but c'mon. He's pitched a grand total of 30 innings as a reliever and he was pretty good. It's hardly some kind of sure thing and it may have caused an injury to boot. Most starters convert better to the bullpen because their stuff isn't as exposed and they are matched up based on their strengths. It's a good bet that any of the guys you listed would also look much more effective as a reliever. How much better or worse than May isn't very clear, not to mention whatever degree better May would be is in a significantly fewer number of innings for the team. I'd much rather roll out Hughes, Duffey, May, Santana, and Gibson in the rotation and let Milone go to the pen. But we seem to have some kind of bizarre obsession with wedging at least one lefty into our rotation at all times.