CSW% is my favorite way to look at elite pitches, and in fact, if you check out our pitch-type leaderboards and sort by CSW%, you’ll see a lot of the nastiest pitches in baseball that you’d expect – Yu Darvish’s slider. Devin Williams’ changeup. Aroldis Chapman’s fastball. It’s a shorthand way to find out what pitches are the best at denying opportunities for hitters to even put the ball in play.
Combined with the ability to filter how often pitches are being thrown, we can also see what pitches we might want to see a little more often based on how effective they’ve been.
I wouldn’t go so far as to say pitchers necessarily should throw these pitches more often. “Should” can do a lot of heavy lifting, perhaps more than we’re willing to insist upon without more in-depth study. I should stop taking handfuls of my kids’ Easter candy every time I walk into the kitchen. That’s a given. But should these pitchers throw these elite offerings more often? It depends greatly on not only the effectiveness of their other pitches but also how those pitches play off of the others in the arsenal.
These pitches do not exist in a vacuum, and so the question of a pitch-mix adjustment can be left to professionals for now. In the meantime, here are three pitches CSW% would like us to definitely see more of. To determine which pitches are the most “under-thrown” from a CSW% perspective, I filtered our 2020 leaderboards for each pitch type that were thrown less than 25% of the time and sorted by the highest CSW% for each pitch.
Slider- Codi Heuer, White Sox; 47.1% CSW, thrown 22.7% of the time
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In 2020, Heuer threw his slider less than a quarter of the time, while hitters managed just a .063 batting average against it. That 47.1% CSW mark was good for third among all sliders in baseball last year. Instead, his major pitch last season was his 97-mph average fastball, which he threw two-thirds of the time for “just” a pathetic .183 batting average against. Hard to go wrong here if you’re Heuer, as his fastball’s CSW% is still a healthy 29.3%, well above average among pitchers in 2020.
Given those offerings paired together, Heuer could be a star in the White Sox bullpen. He’s currently second in the Sox ‘pen in fWAR, and third (behind only Liam Hendriks and Michael Kopech) in xFIP. This season, Heuer has bumped up his slider usage in the early going to 25% of his pitches, and while his season ERA of 4.38 may cause manager Tony LaRussa to lose some faith, that belies a .455 BABIP and 20% HR/FB rate.
In fact, that increased slider usage has led to a higher overall SwStr% and CSW% than his excellent marks in 2020.
Curveball- Brett Anderson, Brewers; 50.7% CSW, thrown 10% of the time
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Anderson already doubled his curveball usage between 2019 and 2020, rising from 5% of his offerings to 10% in that time frame. The pitch worked, generating called or swinging strikes more than half the time he threw it.
Anderson found himself on the injured list after his last start due to a hamstring problem. Although it has only been 17 innings over 4 starts early in the 2021 season, he’s actually reverted to throwing that curve less. It could be that it’s in the early going of the season and he simply doesn’t have a great feel for it yet, or that situations simply haven’t dictated going to it.
Another reason the curve may make less than a tenth of Anderson’s repertoire is that CSW% doesn’t tell the full story of what’s happening behind the pitch. At an average of around 76 mph, the curve isn’t a pitch that “misses” bats. Rather, Anderson relies on it to fool hitters as evidenced from his zero swings and misses on the pitch and an otherworldly 41.2% called strike rate on it. In other words, called strikes are doing the vast majority of work that goes into that CSW% on the curve, so Anderson uses it sparingly as a “fool me once” type pitch.
Splitter- Adrian Morejon, Padres; 41.8% CSW, thrown 16% of the time
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Opposite of Anderson’s curveball, Morejon generates a ton of whiffs (36.4% in 2020) on his splitter. It’s the pitch he throws the third-most, behind his four-seamer and curve, neither of which is nearly as effective as that splitter by CSW% or swinging strike rate.
Adrian Morejon Pitches, 2020
| Pitch | Usage | CSW% | SwStrk% | AVG |
| Fastball | 56% | 27.2% | 6.7% | .333 |
| Curve | 24% | 38.2% | 9.2% | .188 |
| Splitter | 16% | 41.8% | 36.4% | .167 |
In fact, no pitcher in 2020 saw more swings and misses on their splitter than Morejon. He hadn’t even reached the 5-inning mark on the season, as unfortunately he’s slated for Tommy John surgery, but in the early going he increased his fastball usage at the expense of both the curve and splitter. Obviously, that’s too few innings to know what that means for his pitch mix repertoire moving forward, but if he can continue to harness that splitter and curve with elite CSW% he could take another step forward upon his return.
CSW% provides a great look at pitches being effective in different ways. For some, it’s the called strikes, and for others, it’s the whiffs. Taken together though, they provide a lens to view some of the best pitches in baseball whether for analytical purposes, identifying potential breakouts, or simply appreciating the beauty of a veering slider that just touches the zone.
Photo by Matthew Pearce/Icon Sportswire | Adapted by Ethan Kaplan (@DJFreddie10 on Twitter and @EthanMKaplanImages on Instagram)