Joe Kelly’s FIP

Every once in awhile a tweet will catch my eye that simultaneously cracks me up and requires a longer discussion than just the 280 characters on Elon Musk’s hellscape. That was this tweet below.


That is Fielding Independent Pitching

In short it is a formula to help tease out the luck that occurs when a pitcher allows a ball to be put in play. A lot can happen to a baseball when it doesn’t mimic a game of “swift” (which is the game where you paint the batter’s box on the side of a building and play basically a pitcher / hitter one on one game). Especially when the defense behind that pitcher is less than stellar, you know, like the 2022 White Sox.

Anyway, watching Joe Kelly pile up an entire fist full of horrendous performances (I would categorize those as outings with multiple earned runs without completing 1 inning pitched) during the course of the year. While also racking up a ghastly 12.9% BB rate over the season, not even his signature smirk was likely to sway me over to Luke’s camp that Joe Kelly had a “good 2022 season”.

Then I remembered something bad and stupid from the 2018 that gave me deja vu about both FIP and Joe Kelly’s 2022 performance. Thank goodness for MySoxSummer and dumb nicknames.

Enter Bruce Rondon

Picture from

In 2018, the 108 blog / website was pretty young and we were early in our careers of being public idiots and so we thought we needed to do all the kitschy stuff that old media would do, like create nicknames for every player. MySoxSummer and I settled on Super Big Gulp for Bruce Rondon.

This is a fucking stupid name

Anyways, Rondon was coming from Detroit, with a couple of uneven seasons in his rearview mirror. He was also a massive man, lumbering in at a Baseball Reference official weight of 275 pounds (I’d take the over). Bruce could also throw the ball really fucking hard. All of this appealed to us 108ers, so in a lost season, we latched on. The results were disastrous, he threw 29 2/3 innings of 8.73 ERA. He also walked the entire ballpark like Kelly did. Rondon was even worse at 17.5%.

However, he had a 3.73 FIP, which was actually pretty decent and a substantial disparity from his ERA. I always laughed at this because Rondon was terrible and was ostensibly out of baseball immediately after this campaign, so I took it as a signal as to how off-base FIP can be when monitoring single inning relievers in a small sample.

Kelly vs Rondon statistical comparison

Case closed right? Kelly sucked and I can feel confident in my assessment that FIP is imperfect. But just to be sure, let’s run a query and check.

I Saw the Same Eclipse Twice

Below is a query I ran for the last decade plus (back to 2010) for relievers that capture roughly the stats that Kelly and Rondon share in common and all of their peers in this category and I get…..


That’s right, both guys, in the span of 5 years, were with the White Sox and both reminded me of the same weird coincidence in disparity in their FIP and ERA. Let me broaden the search a bit and remove the super high ERA’s from the query.

Just killing their brutal ERA’s out of the query, which is what FIP is supposed to help with, we get a similar group of downright decent reliever performances and some actual outstanding ones! Now, we still have the data point of Rondon being blasted into the sun, but maybe he’s the outlier here and maybe, just maybe, we’ll get GOOD JOE KELLY. Like Actual, GOOD JOE KELLY where it translates into on field results in 2023.

I’ve been a skeptic of Joe Kelly, but Luke’s tweet got me to think this through and see something I wouldn’t have already seen. Luke….


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