Dereck Rodriguez’s success in 2018 was a fun, inspirational story. It also wasn’t going to last.
This isn’t hindsight or complex baseball analysis. It’s fairly simple stuff: If your ERA is 2.81 and your FIP is 3.74 and your xFIP is 4.56, then you’re pretty clearly pitching over your head, and your next year’s ERA is likely to be closer to that FIP or xFIP than to the ERA.
Unfortunately, Rodriguez’s ERA has soared past all the advanced metrics from last year, and his FIP and xFIP aren’t much better. The ERA is an unsightly 4.