Saturday Study Hall, Vol. 1

What is whiff rate and what does it tell us about Royals pitchers?

Saturday Study Hall is a biweekly series defining advanced stats, data and analytics to investigate how they impact the Royals.

Photo courtesy of AP/Charlie Riedel

One of my favorite things about the latest wave of statistics finding their way into mainstream baseball discourse is… they just sound cool. Barrel rate, maximum exit velocity, pitching “swords” — maybe that’s just my inner nerd, but so much of the data we now have readily available measures simple yet vital angles of the game and with fun names, to boot.

Whiff rate is no exception. We’ve long known a pitcher’s ability to miss bats en route to strikeouts is important. It’s so simple it almost feels silly that it’s not a statistic that’s been bandied about longer than just the last decade or less.

So simple, in fact, that this first Saturday Study Hall entry will be relatively short. Some in the future may be longer for more complicated topics but we’ll keep this first one quick and breezy.

Special thanks to Jacob Milham for the idea for this series, which he suggested on Bluesky. If there are specific topics you’d like to see covered in this series or on Royals Data Dugout, please reach out or use the comments section — I want to write about what interests YOU!

Defining Whiffs and Whiff Rate

A “whiff” is exactly what you’d expect: a swing and miss from a hitter.

Whiff rate is simply dividing the number whiffs by the number of total swings. Here’s a look at Lucas Erceg’s Baseball Savant player breakdown from Wednesday’s spring loss to the Giants, in which Erceg was excellent, so you get the idea:

Now, don’t go expecting 60% whiff rates from all your favorite Royals. The average whiff rate is somewhere around 23-25% for starting pitchers; you’ll find strikeout artists in the upper 20s and the game’s truly elite arms, like Cole Ragans, with whiff rates above 30%. Relievers often post a bit higher rates since they can air out their arsenals over an inning or two, hence Astros All-Star closer Josh Hader and Athletics flamethrower Mason Miller posting 40%+ whiff rates to lead MLB last season.

So why do whiffs and whiff rate matter? Well, if you’re here, I’m sure you know the answer to that. It’s impossible for a hitter to do damage on two pitch results: called strikes and whiffs. (Which combine to give us called strikes plus whiff rate (CSW), but we’ll get to that in a later entry in this series.)

If you miss bats at an average or better clip, you can avoid barrels, limit damage and put hitters away.

The Best Royals Whiff Rates

Starting Pitchers

Let’s begin with the starting pitchers as, again, it’s a bit unfair to compare Seth Lugo throwing 90 pitches across six innings to Lucas Erceg letting it rip to three or four batters. The following data is courtesy of Baseball Savant.

1. Cole Ragans, Changeup, 47.8% Whiff — As you saw in the earlier clip, Ragans deploys one of the most devastating changeups in the game — the best, actually. It plummets downhill just before it reaches the plate, helping it rank as the No. 1 whiff rate pitch in MLB among pitchers with more than 150 plate appearances last season.

2. *Michael Lorenzen, Changeup, 46.5% Whiff; Sweeper, 41.4% Whiff — This one requires an asterisk as the elite 46.5% whiff rate on the changeup came only after the Royals acquired him, so it’s a sample of 28.2 innings and 75 changeups. Same with the sweeper, though that weapon is of particular interest — he didn’t use it at all until he came over to Kansas City, ditching his slider for its harder-breaking cousin.

3. Alec Marsh, Sweeper, 46.4% Whiff — No asterisk here, though maybe there should be since Marsh threw this pitch just 5% of the time in 2024. It’s a good offering nonetheless with a 44.3% chase that induces so many whiffs.

4. Michael Wacha, Slider, 37.3% Whiff — The changeup, four-seamer and sinker comprise nearly 70% of Wacha’s offerings, but he does mix in a cutter, curveball and this slider on occasion. It’s a bit of a conundrum, too, carrying an impressive whiff rate while also getting knocked around the park for a .600 slugging percentage.

5. Cole Ragans, Knuckle Curve, 35.2% Whiff — Used around 10% of the time, Ragans typically looks to steal called strikes with the spiked curve when a hitter is expecting something harder. It sees just a 27.2% swing rate from opponents, per FanGraphs, but when they do lift the bat from their shoulders, they have a hard time making contact.

Relief Pitchers

1. Daniel Lynch, Slider, 50.6% Whiff — Now, Lynch did make some starts in 2024, but for the purpose of this exercise, we’re calling him a reliever since most of his work came in the bullpen. The slider was and is a trusted weapon for him in any role, throwing it about a quarter of the time.

2. Carlos Hernandez, Knuckle Curve, 47.1% Whiff — My guess is we’ve seen the last of Hernandez in a Royals uniform, and some team surely will take a chance on stuff like this. He earns 35%+ whiffs on all of his curve, slider and splitter.

3. *Lucas Erceg, Changeup, 44.4% Whiff; Slider, 41.5% Whiff — These marks, like Lorenzen’s, only include Erceg’s time in KC late last summer, but this nasty slowball will play anywhere, anytime.

4. James McArthur, Slider, 42.6% Whiff — Have you forgotten McArthur at one point early last year looked like the closer of the future? The wipeout slider was a big reason why.

5. Sam Long, Slider, 39.7% Whiff — Long’s slider is filthy with a 116 Stuff+, hence why the Royals asked him to back off his fastball usage in 2024 to double his slider usage. It worked to great effect with the left-hander enjoying the best season of his four-year career.

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With Opening Day just around the corner, stay tuned this coming week for a final recap of the best Statcast performers from this spring and my season predictions on Thursday before the festivities begin.