Kershaw’s Slider Gets Even Nastier

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OK, now Clayton Kershaw‘s just being vindictive. The 26-year-old lefty, fresh off earning his second career Cy Young Award and signing the richest pitching deal in MLB history (seven years, $215 million), has brushed off an early-season back ailment and is inflicting nearly unprecedented pain on opposing batters.

He recently reeled off a 41 inning scoreless streak, the longest in the majors since Brandon Webb tossed 42 spotless frames in 2007 and tied with Luis Tiant for fifth-longest during the Expansion Era (1961-present). Kershaw’s 1.59 Fielding Independent ERA (FIP) is the lowest ever for a starting pitcher throwing 90-plus inning during the live-ball era (1920-present), save for Pedro Martinez‘s 1999 campaign (1.33). And his 9.69 strikeout-to-walk ratio is fourth-highest among hurlers meeting those criteria, trailing just Bret Saberhagen (11 K/BB ratio in 1994), Ben Sheets (10.55 in 2006) and Cliff Lee (10.28 in 2010).

Kershaw was already the game’s pre-eminent pitcher, but now he’s making major league hitters look like the poor souls tasked with facing him on the Texas prep scene. He’s accomplishing that by refining an already-sinister slider. How has Kershaw improved his nearly-perfect out pitch? Let’s count the ways.

He’s hammering hitters at the knees: Kershaw’s throwing 68.4% of his sliders to the lower third of the strike zone in 2014, up from 48.1% last season. The pitch is most effective when spotted at hitters’ knees: he’s got a career .161 opponent slugging percentage on low sliders, compared to .372 on middle-plate sliders and .267 on high sliders.

He’s expanding the strike zone:  Hitters are chasing Kershaw’s slider out of the zone 50.2% of the time this year, up from 40.7% in 2013. No starter throwing at least 200 sliders this season comes close to matching Kershaw’s zone-stretching ability. Colby Lewis (46.3% slider chase rate) and Corey Kluber (43%) are a distant second and third on the list. Kershaw induced lots of chases on low-and-away sliders in 2013, but hitters are swinging even when the pitch practically hits home plate in 2014

Opponent swing rate vs. Kershaw’s slider, 2013
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Opponent swing rate vs. Kershaw’s slider, 2014

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He’s generating more wind power: Kershaw is getting swings and misses 53.5% of the time with his slider, a marked increase from 41.1% during his comparatively paltry Cy Young-winning 2013 season. He owns the highest slider miss rate among starters, topping Max Scherzer (50%) and Ervin Santana (46.4%).