Pittsburgh Pirates: Unluckiest Pitches of the 2023 Season

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Which Pittsburgh Pirates pitchers suffered from bad luck on their offerings during the 2023 season?

There are so many ways to evaluate and analyze MLB players in today’s game. With the implementation of Statcast in 2015, and subsequently Baseball Savant as a database for Statcast, every pitch and every batted ball, along with their metrics, defensive positioning, and everything in between has been logged since 2015. Many stats, such as xwOBA, or expected weighted on base average, have been created by using these metrics. Since these stats such as xwOBA have a predictive factor to them, it’s been easier to identify luck in baseball.

What I want to use xwOBA for today is looking at the outcomes of pitches thrown by Pittsburgh Pirates pitchers, and examining who was the unluckiest in 2023. The lower the expected wOBA, and the higher the actual wOBA, the more unlucky the Pirates’ pitcher’s offering was.

Before we get into our first players, let’s give a brief rundown of what these stats are. wOBA, or weighted on-base average, is what many consider a better alternative to OPS. OPS weighs a hit and the walk as the same thing. It also solves the issue of those who don’t agree that a double is twice as valuable as a single. Each walk, HBP, single, double, triple, and home run is scaled differently. xwOBA, or expected weighted on-base average uses exit velocity, launch angle, sprint speed, to estimate what the wOBA of a player or outcome should be with these factors taken into account.

Quinn Priester’s Slider - wOBA: .425, xwOBA: .339

Quinn Priester struggled in his first call-up to the big leagues. Although he looked slightly better in his second go around, Priester still struggled overall. But he only just turned 23 in mid-September. But one of his more promising developments was his slider, which while knocked around the park, certainly showed potential as an above average offering.

Opponents had a .295 batting average, .659 slugging percentage, and .425 wOBA against his slider. However, it had some aspects that made it look like it could be a reliable pitch in the future. The first is his 41.4% whiff rate. Of the 454 pitchers who used a slider in at least ten match-ups, Priester had the 76th highest whiff rate. That was higher than standout starting pitchers like Merrill Kelly, Kodai Senga, and Braxton Garrett.

The second reason is the expected numbers looked a lot better. Batters had a .250 xBA, .439 xSLG percentage, and .339 xwOBA when facing Priester’s slider. That’s a lot better than batting nearly .300 with a SLG percentage above .600, and wOBA above .400. Now granted, .339 is still below average. However, it’s a difference of nearly 86 points. That is a Grand Canyon-sized gap.

Bailey Falter’s four-seam fastball - wOBA: .347, xwOBA: .305

The Pirates acquired Bailey Falter at the trade deadline in a one-for-one swap with the Philadelphia Phillies for infielder Rodolfo Castro. Falter’s fastball has some very deceptive attributes, including velocity that plays up because of his long release point, and his high active spin rate. But the pitch should have played better than it did in 2023.

Falter’s four-seamer saw opponents hit .305 with a .438 slugging percentage, and .342 wOBA. He only had a 15.3% whiff rate with the pitch, but a look under the hood reveals that his fastball could have been much better. He registered a .266 xBA, but an elite .375 xSLG percentage. On top of that, he had an xwOBA of just .305.

The difference between a .342 wOBA, and .305 wOBA is massive. Ten players had a wOBA between .340-.343. They all had a league/park adjusted wRC+ around 120. The two players who had a .305 wOBA, Cincinnati Reds’ players Elly De La Cruz and Tyler Stephenson, had a wRC+ of 84 and 85, respectively. That is a 35% difference in production.

Mitch Keller’s Sinker - wOBA: .309, xwOBA: .293

Mitch Keller added a sinker to his arsenal last year. The pitch was arguably his saving grace in 2022, and it continued to be an effective offering in 2023. However, even though it was a reliable pitch in Keller’s arsenal, it could have been even better.

Keller’s sinker held batters to just a .258 batting average, but .346 wOBA, and .309 wOBA. When opponents made contact with the pitch, they had just a 86.7 MPH exit velocity against it, well below the league average rate. But a deeper dive shows just how good this pitch can be. While his xSLG percentage with his sinker was still roughly the same at .342, his xBA drops to .236. Meanwhile, his expected wOBA sinks below .300, down to just .287 (no pun intended).

We already looked at what a wOBA around the .300 looks like with Falter’s fastball, but what would a wOBA well below that look like? Well, it would look like Yuli Gurriel, Yasmani Grandal, or Isiah-Kiner Falefa in 2023. Their wRC+ ranged from 77 to 82. FanGraphs describes a wOBA of .290 or lower as “awful” while .300-.310 is between poor and below average.

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