Does Montgomery have a track record of outperforming his xFIP/SIERRA?
Yes - at least xFIP. On average by about half a run each season (ish). At least depending on if one considers 2020 a real season or not (I do not, YMMV).
https://www.fangraphs.com/players/jordan-montgomery/16511/stats?position=P
FWIW, I was actually curious about the whole xFIP thing with Montgomery (the "thing" being that he's outperformed his peripherals the last three years). I looked through his stats to see if there was something that stood out in his batted ball stuff that indicated why he might have overperformed his peripherals.
(Dunno if this is helpful to anyone else, but I figured that since I found it, I might as well share it.)
The short answer, I suppose, is no.
The long answer is that the reason seems to change every year.
To wit: looking at how many balls allowed in play were soft/medium/hard contact, he had the following:
Year: S%/M%/H%
2021: 20.6% /48.0% /31.4%
2022: 15.1%/56.9%/28.0%
2023: 14.3%/53.5%/32.2%
AL averages:
2021: 16.3%/51.5%/32.1%
2022: 16.2%/53.6%/30.2%
2023: 15.5%/52%/32.5%
So in 2021, he had a whole lot more soft contact than the league. In 2022, he had more medium contact and less hard contact. In 2023....nothing stands out.
So what happened in 2023? Well here's HR/FB:
YEAR: Montgomery/AL Average
2021: 11.8% /13.8%
2022: 13%/11.4%
2023: 9.3%/12.5%
which may be related to where the balls were hit:
YEAR: Pull%/Center%/Oppo%
2021: 40.1%/37.2%/22.6%
2022: 38.7%/36.2%/25.1%
2023: 39.2%/33.1%/27.7%
AL avg:
2021: 40.2%/34.7%/25.1%
2022: 41.0%/34.4%/24.5%
2023: 40.1%/35.0%/24.9%
So a bunch more opposite field contact...in the year where the pull-side overshift was banned. Notably, flyballs hit to the opposite field are much less likely to go over the wall - just to pull some random data off of SB Nation's
Crawfish Boxes from 2013:
I have no idea if this is all sustainable or happy accident, but it at least gives some context to what was happening with Montgomery and his xFIP.
