2. Jordan Montgomery
The only reason Jordan Montgomery is not #1 on this list is his lack of team control. Monty is a free agent at the end of this season. There is also a bit of a concern with his current injury, though not much.
Aside from these two detriments, Jordan Montgomery has been an ace-caliber starter for a year and a half now. Before his trade to the Cardinals, Montgomery was a middle-of-the-rotation guy who could buy you 160-175 innings a year and always give the team a chance to win. Since the trade, he has been at the top of the National League in all major stats for starters.
This year, Jordan has a 3.23 ERA, 3.52 FIP, 1.223 WHIP, and has pitched into the sixth inning in all but two of his eighteen starts. He is just below league average for strikeout rate, but he excels at limiting walks and hard hits. He has high groundball rates and should pitch very well with a strong defense behind him. Many teams will be calling asking about free-agent-to-be Jordan Montgomery.