Statcast Slider Usage Studs and Duds for Week 20

Welcome back to RotoBaller’s pitchers advanced stats and StatCast studs and duds article series! Each week we will select an advanced stat, choose two studs and two duds, and analyze what those stats could mean for future fantasy output. Last week I used Statcast's pitch arsenal tab to look at starters' four-seam fastball usage and this week I will do the same for slider usage.

Pitchers' secondary pitches need to be strong in order to achieve high strikeout rates, a metric that matters greatly to fantasy players, so it is worth identifying those starters who can rely on their secondary pitches.

I will pick two high-volume slider pitchers who have done well this season and two who have not or are slumping recently. Let's get into it!

Slider Studs

All stats current as of 8/12/19, courtesy of Baseballsavant.com 

Clayton Kershaw - Los Angeles Dodgers

39.7% slider usage

Our first pitcher needs no introduction; he has been one of baseball's best pitchers for many seasons. Clayton Kershaw has been great once again this season, going 11-2 with a 2.77 ERA, 1.04 WHIP, and 25.4% K rate. While he is known for his looping curveball, Kershaw's main secondary pitch is his slider, which he throws almost as much as his fastball. Let's take a look at this pitch and how it has helped Kershaw.   

Kershaw's slider is so effective thanks in part to its high spin rate (2,674 revolutions per minute). That mark is third-highest among pitchers who have thrown the pitch at least 500 times this season. Kershaw's numbers against the pitch reflect how good it is; his .217 batting average against, .230 expected batting average against, and 18.3% swinging-strike rate are all stellar.

There isn't a ton to analyze here, as most fantasy players know that Kershaw is an elite option. However, it is surprising to see how frequently he relies on his slider. It makes sense as his fastball is not overpowering, but Kershaw is typically known for his curveball (which is also a great pitch). So long as he can stay healthy for the rest of the season, Kershaw will continue to help fantasy teams into the playoffs.

Patrick Corbin - Washington Nationals

36.9% slider usage

Our second pitcher blew up in 2018 because of his nasty slider and has continued to bring it this season. Patrick Corbin relied heavily on his slider last season and some people in the fantasy community were worried that he would not be able to continue to find success using it so much, but he has shown that the pitch really is that dominant. Corbin is 9-5 with a 3.41 ERA, 1.15 WHIP, and 28.6% K rate this season. Let's look at his unusual but effective usage of the slider.

Corbin actually uses the slider as his primary pitch, throwing it more than his sinker (36.9% vs 33.9% usage). The slider is clearly his best pitch; Corbin has a .171 batting average against, .153 expected batting average against, and an insane 26.3% swinging-strike rate. Corbin gets an above-average 2,406 revolutions per minute spin rate on the pitch, causing it to drop about an inch more than the average slider. The pitch is one of baseball's best, which is why Corbin has become a higher-end fantasy option.  

Fantasy players aren't wrong in questioning whether a starter could be successful with a non-fastball primary pitch, but Corbin has shown that it can be done for almost two seasons now. He did scuffle at the start of the season but is locked in now, playing well for a Nationals team that is fighting for a playoff spot. Fantasy owners should feel comfortable relying on Corbin and his slider down the stretch.

Slider Duds

All stats current as of 8/12/19, courtesy of Baseballsavant.com 

Chris Sale - Boston Red Sox

38.3% slider usage

Our third pitcher is in the same top tier as Kershaw but has not performed like it this season. Chris Sale has gone 6-11 with a 4.41 ERA, 1.09 WHIP, and 35.3% K rate. His numbers are excellent other than his ERA, but that won't make fantasy owners feel better. The top concern coming into the season was Sale's health and, while he does appear to be healthy, his fastball velocity has dropped. Consequently, Sale has relied even more on his slider (38.3% usage vs 36.1% fastball usage). There is still time for Sale to potentially help fantasy owners, but what should they expect from him?

Fortunately, all signs point to Sale still being a fantasy stud. His fastball is still quite an effective pitch, but his slider is even better, so it has been a smart transition in using it more. He gets a spin rate of 2,486 revolutions per minute on the pitch, causing it to move a ton (vertical drop of 4.8 inches above league average, horizontal break of 2.9 inches above league average). Consequently, he has a .204 batting average against it, a .172 expected batting average against, and a 17.1% swinging-strike rate.

Further, several signs point to Sale just being unlucky this season. His .312 BABIP is higher than his .293 career mark and his 3.01 SIERA is much lower than his ERA. Overall, Sale still shows all the signs of an elite pitcher, thanks in part to his elite slider.  Unfortunately, he has gotten unlucky, but fantasy owners should not be deterred. given how he has pitched.

Matthew Boyd - Detroit Tigers

37.4% slider usage

Our final pitcher had a huge amount of hype surrounding him in the beginning of the season but has had mixed results since. Matthew Boyd has an impressive 31.9% K rate, but he also has a mediocre 4.16 ERA and 1.17 WHIP. The K rate can be attributed to Boyd's fastball-slider combo, which are pretty much the only two pitches he throws. Does Boyd have what it takes to improve his ERA as well as his K rate?  

Boyd gets a lot of spin on both his fastball (2,390 revolutions per minute) and slider (2,365 revolutions per minute), which has helped him get away with throwing basically two pitches (48.7% fastball usage, 37.4% slider usage). His 19.5% swinging-strike rate on his slider is particularly impressive. Also, like Sale, his 3.34 SIERA is lower than his ERA and his .315 BABIP is higher than his .298 career mark.  

Many signs point to Boyd getting unlucky this season based on his underlying numbers. However, this is the first season that he has found success. I had difficulty trusting him in the beginning of the season based on his history and still feel the same. I could understand fantasy owners relying on him now as they have all season long, but I wouldn't want to leave the fate of my fantasy season on his arm. 

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