Robert Stephenson’s Slider, and the Paradigm Shift in Motion

Normally I don’t write about bad players. It’s more of a truism than anything: writers like to analyze the breakout or peak-performance potential of top prospects or, alternatively, red flags associated with the game’s premier talents. Rarely do we write about objectively bad players.

Through 120 Major League innings (and change), Robert Stephenson has been an objectively bad starting pitcher, having compiled a 5.10 ERA, an anemic 1.63 strikeout-to-walk ratio (K/BB), and 0.1 WAR. A former 1st-round pick and a consensus top-100 prospect for four consecutive years, Stephenson quickly fell from grace after a catastrophic small-sample debut in 2016. Entering his age-25 season, though, he still has plenty of time to turn things around.

That’s the beauty of baseball: an objectively bad player can become an objectively good one, sometimes overnight. 2017 was a banner year for post-hype prospects, all of whom seemed, at one point or another, destined for eternal mediocrity and former-prospect bustitude. I think Stephenson can become an objectively good pitcher, but it’ll take work.

Here’s a top-10 list, presented ordinally and without the statistic by which I’ve ordered it, of pitchers who accomplished something in 2017, from a list of hundreds of other data points:

  1. Corey Kluber
  2. Carlos Carrasco
  3. Max Scherzer
  4. Stephen Strasburg
    Danny Salazar
  5. Clayton Kershaw
  6. Zack Greinke
  7. Nathan Karns
  8. Dallas Keuchel
    Robbie Ray
  9. Dylan Bundy
    Blake Snell
  10. Stephenson

That’s a healthy list. Perhaps Karns seems out of place here, but if you paid attention to his April prior to thoracic outlet surgery (ugh), you’d know it was excellent. If you need a preposterously cheap lottery pick in the late rounds of deep leagues (or any format, really), keep in mind Karns, whose 27% strikeout rate (K%), 7% walk rate (BB%), and 50% ground ball rate (GB%) momentarily dazzled us.

Sorry — distracted. So, Karns might seem like an outlier, but he’s not. Same with Bundy and Snell, too, but Bundy has been a serviceable (a term used loosely here) starter for two years; Snell, more so, with a promising second half of 2017. No one is truly out of place — no one, that is, except Stephenson.

Here’s how that list looks in full, and tabulated:

Whiff Rates by Individual Pitch, 2017
Name Pitch Whiff Rate (SwStr%)
Corey Kluber Slider 29.3%
Carlos Carrasco Slider 27.3%
Max Scherzer Slider 27.0%
Stephen Strasburg Change 26.9%
Danny Salazar Change 26.9%
Clayton Kershaw Slider 26.5%
Zack Greinke Slider 26.4%
Nathan Karns Curve 26.1%
Dallas Keuchel Change 25.7%
Robbie Ray Slider 25.7%
Dylan Bundy Slider 25.2%
Blake Snell Slider 25.2%
Robert Stephenson Slider 24.6%
SOURCE: Baseball Prospectus, c/o PITCHf/x
Min. 200 thrown

Turns out sliders and change-ups can be really good pitches, and Karns threw an electric curve in 2017. And there, with the 13th-whiffiest pitch of 2017, is Stephenson. More incredibly, he didn’t start throwing the pitch until last April, and he didn’t throw it regularly until July, after returning from an 8-start demotion to Triple-A. Stephenson basically introduced and developed his best pitch on a whim. Moreover, he knew it was good. From July 22 onward, in 12 starts during which he threw his slider 27% of the time (and his now-abandoned curve 3%), he posted a 3.30 ERA and struck out 22.5% of hitters.

Unfortunately, during that span, he also walked 14.1% of hitters and compiled a 1.42 WHIP. The outputs (good) didn’t match the inputs (bad), and for that, he should consider himself lucky, fortunate, grateful, what-have-you. 2017 could have been equally disastrous to 2016.

That’s why the aforementioned lists are interesting, why Stephenson is so odd (to me, at least): he has been incredibly bad despite joining mostly elite company. The best pitchers in the game throw the best pitches, and some of the others who aren’t the best show glimpses of brilliance now and again, with promise for more. Stephenson has one of the game’s best pitches with some of the game’s worst outcomes. It all boils down to command: no one succeeds walking more than five hitters per nine innings (BB/9) as he did after last year’s All-Star Break. Throwing the worst rate of 1st-pitch strikes (F-Strike%), second only to the wildly mediocre Chris Tillman, he of the 7.84 ERA last year, certainly does not help, nor bring comfort, nor inspire optimism.

Yet there’s something about Stephenson I can’t shake. If he could make one of baseball’s smartest, albeit lowest-key, adjustments in 2017, perhaps he could make another in 2018. He doesn’t need much in the way of “stuff;” his change-up is also above-average, bordering on plus. It’s his four-seamer, which he threw for more than half his pitches, that was incredibly detrimental, allowing a .580 slugging percentage (SLG) to opposing hitters. You’ll be hard-pressed to find a worse fastball. (His slider, meanwhile, allowed a .211 — .211! — slugging percentage.)

Alas, it may behoove Stephenson to maybe not throw his four-seamer so much, especially if he can’t spot it. He has two excellent secondary offerings he could, and should, convert to pseudo-primary offerings (while still throwing his fastball, of average velocity, to keep hitters honest). Stephenson ranks in the lower 15% of pitchers in terms of zone frequency (Zone%), but so do Snell, Greinke and Keuchel. Stephenson can succeed with erraticism, whether intentional or accidental. He just needs to get ahead in the count, and that means learning to trust his off-speed pitches to lead off a plate appearance.

To attest: his fastball, which he threw 65% of the time in 0-0 counts, recorded 1st-pitch strikes 25% of the time. His slider, thrown 16% in such counts, notched strikes more than twice as frequently (53%). In plate appearances that started 1-0, Stephenson allowed a .409 wOBA (7.23 xFIP). In those that started 0-1: .314 wOBA (3.41 xFIP). It’s absurd, the Jekyll-and-Hyde nature of his proficiency if he’s ahead or behind. I’m sure the narrative runs parallel to most other pitchers, but most other pitchers don’t need marginal improvements as desperately as Stephenson does.

The good news is Stephenson is already on the right track, having decreased his usage of 1st-pitch fastballs more than 10 percentage points upon returning from his demotion. The adjustment shows some semblance of a paradigm shift and, again, suggests he’s aware how effective his new, elite pitch truly is. Sure, he still walked a ton of hitters in the second half last year despite trusting his stuff more. But he also cut his walk rate down to 8.6% when starting ahead in the count — and, as aforementioned, he started ahead in the count more often from July onward.

You have to squint hard to see it, but there’s promise here — something like a poor man’s peak Francisco Liriano redux, or a cheaper Dinelson Lamet. (I’m not an expert in mechanics, but these seem like reasonable projectable ceilings — emphasis on ceiling, not to be construed with nebulous upside — for Stephenson given no discernible progress with his control.) The farther Stephenson steers from his fastball, the more his baserunner-prevention capability, in terms of both strikeouts and walks, grows. Once a dynasty throwaway, he’s now a sneaky bet to breathe life into his long-term value and demonstrate at least some of the potential that prospectors saw in him for nearly half a decade.

Stephenson faces long-shot odds to pay off in 2018. This is not your obviously imminent breakout like Ozzie Albies, Ronald Acuna, Willie Calhoun, et al., nor is he a flashy gamble with sky-high upside But with an average draft position (ADP) of 453rd overall in the National Fantasy Baseball Championship (NFBC), there are worse late-round dart throws. I’ll draft Stephenson as bench depth with dreams of him evolving into Liriano of a former life, i.e., an arm of mid-rotation caliber; if he crumbles, no sweat. But it appears he knows he’s onto something, and those are some coattails I’m eager to ride.

Currently investigating the relationship between pitcher effectiveness and beard density. Two-time FSWA award winner, including 2018 Baseball Writer of the Year, and 8-time award finalist. Featured in Lindy's magazine (2018, 2019), Rotowire magazine (2021), and Baseball Prospectus (2022). Tout Wars competitor. Biased toward a nicely rolled baseball pant.

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4 years ago

It seems to me that Ks and BBs go hand-in-hand. To that end, wouldn’t a guy with some of the worst command in baseball happen to miss bats with a pitch?

It isn’t shocking to me at all that a guy would have a great pitch and be a bad pitcher – I can’t imagine that doesn’t describe lots of minor leaguers and relievers. That is pretty much what makes major leaguers starting pitchers. Its a bit like the the golfer that can hit a drive, but has little interest in putting – not good at golf. I doubt this is a golf community, but you get the idea…