Luke Gregerson’s Re-Disappearing Slider

Luke Gregerson owns one of the best sliders in baseball, and when it’s working, he is tough to beat. The pitch that brought him to San Diego in March 2009 has made him an integral part of the Padres bullpen ever since.

Kevin Towers acquired Gregerson from the Cardinals as the player to be named later in the trade that sent Khalil Greene to St. Louis. Towers did so thanks in large part to former Padres outfielder John Vander Wal:

Then Vander Wal uttered the words Towers won’t soon forget, words that right then and there essentially sold the then-Padres general manager on relief pitcher Luke Gregerson and his devastating slider.

“He said it disappears,” Towers said.

Gregerson, a former 28th-round draft pick, promptly made the unexpected jump from Double-A and enjoyed a strong rookie campaign. He was even better as a sophomore, turning opposing batters into Don Drysdale or Liván Hernández–excellent hitting pitchers, but not consistent threats.

Then came 2011 and a disturbing downturn in strikeouts, from 10.2 to 5.5 K/9. Manager Bud Black blamed an “ineffective slider,” with the dearly departed Friar Forecast corroborating Black’s assessment, noting that hitters were not missing the pitch as often as in previous seasons. Gregerson’s slider no longer disappeared.

Still, pitching coach Darren Balsley observed that Gregerson “found out how to get outs in different ways.” And while it is good to have a backup plan, it is better to not have to use that plan.

Fortunately, Gregerson’s slider reappeared. Or rather, it re-disappeared. As I wrote in his player comment for Baseball Prospectus 2013:

Last year we suggested that Gregerson needed to “rediscover the tilt on his slider” for continued success. He did, and the results were spectacular. He subtracted velocity, replacing it with more horizontal and vertical movement. [This should read “less vertical movement”; the error is mine. -gy] He also leaned on the slider more than ever before, throwing it two-thirds of the time (three-quarters of the time against right-handers).

This improvement was no accident. Last August, Gregerson said of his slider that he “worked on it a lot last season and this season,” and that he had a good enough feel for the pitch to throw it “pretty much at any point in time.” He does throw it often, and it has evolved over the years (values are taken from his PITCHf/x Player Card at Brooks Baseball):

Year Freq (%) Velo (mph) pfx HMov (in.) pfx VMov (in.)
2009 50 84.02 5.00 1.85
2010 58 84.66 2.10 1.56
2011 55 85.51 -0.12 1.22
2012 66 83.54 3.11 0.01
2013 58 81.46 4.40 -0.51

HMov is horizontal movement, VMov is vertical movement.

This is an oversimplification based on aggregate numbers, but the pitch is slower, less downward, and more side-to-side than it used to be. Our pal Eno Sarris at FanGraphs dug deeper and found that Gregerson throws at least three different sliders that each have different characteristics.

Such variation also helps explain the lack of severe platoon splits we might expect from someone who relies so heavily on a pitch normally associated with dominance against same-handed batters. Tougher against righties, who hit like Warren Spahn against him, Gregerson is no slouch against lefties, whom he turns into Damian Jackson.

Padres Public’s VM Nate noted in the comments of Sarris’ article that Gregerson is like a knuckleballer who throws what is classified as a single pitch in a variety of ways. And like a knuckleballer, Gregerson uses his specialty pitch as the foundation for all others. Or as he tells it, “I set up my fastball with my slider.” Depending on the situation, Gregerson might alter the break on his slider, giving the man in the batter’s box much to contemplate while awaiting the pitch.

Extending Myron Logan’s work at Friar Forecast (and Hardball Times), here are called strikes, swings, and whiffs/swings on Gregerson’s slider over the years:

Year Call Str. (%) Swings (%) Whiffs/Swings (%)
2009 15.6 55.4 46.7
2010 17.6 53.5 41.0
2011 13.3 52.7 34.1
2012 17.2 53.4 41.5
2013 17.6 49.4 35.7

Gregerson is mostly continuing the trends he exhibited last season. The called strikes, which plummeted in 2011, returned to 2010 levels last year and have stabilized. The swings are down slightly this year, as are the whiffs/swings.

The rightmost column bears watching. If it ends up near 40 percent, batters will have their hands full. Even if it doesn’t, he should remain effective. As Balsley noted when the slider went missing in 2011, Gregerson compensated with improved “knowledge of how hitters hit in certain counts” and learned how to mix in his sinker more. He made adjustments.

Knowledge is good. A disappearing slider is better. Equipped with both, Gregerson is tough to beat.

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How much do you love Luke Gregerson’s slider? Leave a comment, send an email (, or hit me up on Twitter (@ducksnorts).

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  • LynchMob

    The concept of “adjustments” is amazing … so many knobs that can be turned … and certainly as time passes and skills change, some of them have to be turned … and it also seems like even if/when skills don’t change, knobs need to be turned because the hitters have made adjustments …

    Interesting to see such success at 81 mph … and I wonder what negative VMov means (especially at that slow of a velo)?

    • Geoff Young

      LM, the ability of elite athletes (or performers in any area) to adjust even as they are operating at such high levels blows my mind. It’s difficult to comprehend how hard what they’re doing is because they make it look so easy.

  • Awesome article. Tons of information that is well presented and accessible.

    Love all the hat tips to Myron, too. That guy was my introduction to sabremetrics.

    • Melvin

      I miss Myron :/

      • I so badly want to know what he thinks about Michael Morse. He’s the rich man’s Russel Branyan, right?

    • Geoff Young

      Thanks, John… glad you enjoyed the article. And Myron did great work. I hope he resurfaces someday to grace us with more of it.

  • Good stuff, Geoff. I look forward to tracking that Whiffs/Swings (%) as the season goes.

  • Jeremy_Nash

    Love this article. Great read on a topic that I have been wondering about the past couple years. As always Geoff, you knocked it out of the park (or caught us looking in this case).

  • ballybunion

    I’m late to the party again! Nice article, though I’m surprised you didn’t mention the oblique strain that put Gregerson on the DL in 2011. Having suffered that injury, I know how debilitating it can be for an extended period, and how subtle adjustments for it can damage athletic performance. My oblique strain killed my golf swing for nearly a year, and I can only imagine what unconscious changes could creep into a pitching motion.

    • Geoff Young

      You raise a good point. A quick check of Gregerson’s slider velocity and movement before and after the DL stint reveals nothing unusual, but this doesn’t mean he suffered no lingering effects as a result of the injury.

      As you note, it’s easy to compensate when something doesn’t work as it should. Plus there could have been command issues after the month-long layoff.

      Thanks for adding to the discussion!