Clayton Kershaw: Newfound Effectiveness by Injury or Intent?
“That was a totally different Kershaw than I've ever seen," said Braves first baseman Freddie Freeman said after Atlanta’s Game 2 loss in the NLDS. "Usually, he's at 94-96 mph with an 88-mph slider and a big curveball. I saw one curveball tonight and I saw 90 mph heaters. It was just kind of weird. We were hitting the ball in play. We were just hitting weak ground balls and popups.”
Clayton Kershaw has been a Major League pitcher for 11 seasons now. His 6’4 frame, $215 million contract, 153 career wins, sub-3 ERA for his career, and 2,275 strikeouts can be quite an intimidating factor when batters step into the box. Best known for his big breaking curveball, Kershaw has been a force in the National League West for just over a decade. But what has this season’s Clayton Kershaw different from years past?
To start, his average fastball velocity has been drastically declining since the 2015 season. The 94-96mph Kershaw that Freeman was use to seeing is gone and instead, he’s incorporated a slower fastball, with more spin, and has been utilizing his slider more to get ground ball outs instead of strikeouts. As for his curveball, it is now registering 15mph slower than his slider, averaging 73mph this season.
Once Statcast was introduced in 2015 and spin rates officially became a measurement of revolutions per minute that a baseball makes when released, the Dodgers and their analytics team started incorporating it into Kershaw’s repertoire. As noted above, there is a significant increase in spin rate from 2015 to 2016, once the measurements started. The next significant increase we can see is Kershaw’s slider from 2017 to 2018, jumping well over 100 more revolutions than the year prior. His fastball has been increasing year by year as well and is just 50rpms behind his curve.
This next graph represents fastballs, curveballs, and sliders thrown by Clayton Kershaw as well as groundouts they’ve recorded over time. The major finding here is the amount of groundouts induced by Kershaw’s slider from 2017 to 2018. They spiked from 44 groundouts in 2017 to 96 this season. He is getting more hitters to chase low in the zone on his high spin rate slider, resulting in weak outs.
This next chart shows the breakdown of the three major pitches thrown by Kershaw over the span of his career. Notice how the lines are starting to trend closer together up through this season on his fastball and slider. He is now throwing almost a dead even split of sliders compared to fastballs, something unusual for a starting pitcher.
Kershaw’s curveball usage is decreasing, almost becoming obsolete. His fourseam fastball is being used 44% of the time, slider 39.1%, and curveball 16.1%. The three time Cy Young award winner is still producing ace caliber numbers on basically two pitches.
Here is the breakdown of all fastballs and sliders thrown throughout Kershaw’s career and the differential by season.
Clayton Kershaw’s decreased fastball velocity could have been a result of the back issues he’s been experiencing this season, but despite not dominating with his 96mph fastball he once had, he has now found new success in using his slider more often and is focusing on getting weaker outs rather than blowing people away. From the perspective of pitch tunneling, this may be more effective. Two pitches at the same velocity, with different movement may prove to be more effective. In 2018, Kershaw’s fastballs and sliders accounted for 83% of his total pitches, his fastball now at 90 mph is harder to recognize behind the 88m mph Slider. Below is a 3D visualization from Baseball Savant that depicts exactly how Kershaw is attacking hitters with his new approach.
Visual Key: Green - Release point | Yellow - Pitch Recognition | Purple - Swing Decision
For Kershaw whether by injury or intent, his pitches are tougher to recognize and late movement on both pitches have proven to induce weak contact early in the count. His stat-line speaks for itself, 8.65 K/9 ratio is the lowest it’s been in ten seasons, but his ERA is still a highly respectable 2.73. His ground balls per fly ball (GB/FB) ratio is 1.62, up from 1.45 last season. It may not be the Clayton Kershaw we’re use to seeing, but the results don’t lie. He’s still just as dominant as ever.