Philadelphia Phillies pitcher Aaron Nola
Now I have written in the past about Nola being a free-agent starter that the Cardinals should avoid, but out of all the options on the Phillies that are going to be free agents, he's undeniably the best option.
Nola definitely has had a solid career, he's a 200-innings-a-year kind of guy, he gets swings and misses, and has top-of-the-rotation stuff. But he has struggled this season with home runs, walks, and pitching away from Philadelphia which has contributed to an ERA over 4 over the last 3 seasons.
I also believe that Nola will stay with the Phillies barring something changes between now and the start of free agency. My personal opinion is that there are better options, but I wouldn't be totally against it if Nola was brought in by St. Louis this winter.