How would you explain the three plus year pattern of outperforming his FIP? I agree that he doesn't really give up enough ground balls to fit that profile, but three plus years in a row is hard to attribute to good luck.
My best guess is that the HR component overstates the FIP for guys who don't give up a lot of base runners.
Julio is a guy who has outperformed his FIP. That is expected but not by a near full run that it is right now. So some regression is expected but not to a 3.7 ERA. I mean his BABIP against is in the 240's. That's unlikely to be sustained the entire year. The same is especially true for Wisler who's BABIP against is 232. That is very unlikely to continue as well. Just some things to keep in mind.