It’s not often that a pitcher has a sub-2.00 ERA and has both a lower FIP and xFIP but that’s the trifecta that new Mets closer Edwin Diaz pulled off last year. In 73.1 IP, Diaz had a 1.96 ERA, a 1.61 FIP and a 1.78 xFIP. A 15.22 K/9 certainly helps in all three categories, as does a 2.09 BB/9.
If you want to nitpick, you can say he’s only a one-inning guy. In 73 appearances last year, only three times did he get four outs in a game and he never pitched more than that. But hopefully the Mets’ pen will be comprised of multiple other guys who can get six outs at a time and make that a moot point.