Jacob deGrom’s Strikeout Spike

Jacob deGrom has been one of the better and most consistent pitchers in the league across his short career, posting ERAs of 2.69, 2.54, and 3.04 in 2014-2016. He accumulated a 12.0 WAR in those seasons, 13th in the league and sandwiched between Dallas Keuchel and Stephen Strasburg. Good company.

He has been great, but he has not exactly been a strikeout maestro. He averaged 9.24 K/9 in 2014-2016, a good mark and solidly above the league average of 7.86 in that time, but also nothing to write home about. However, his K/9 has skyrocketed to 12.66 in 2017, ranking 3rd among qualified starting pitchers. What is behind the spike?

First, here is a table of deGrom’s pitch usage across his career:

Season Fastball (FF)% Fastball (FT)% Slider% Change Up% Curveball%
2014-16 45.4% 16.0% 17.0% 11.5% 10.0%
2017 48.1% 11.4% 24.3% 9.6% 6.6%

In 2017, deGrom has thrown considerably fewer two-seam fastballs and made his curveball an afterthought, greatly increasing his slider usage. In 2016, deGrom’s most effective strikeout pitch was his slider, with a 27.5% K%. His two-seam fastball induced the fewest strikeouts by far, posting just a 13.1% K%. deGrom has also slightly increased his four-seam fastball percentage, which has been his second-most effective strikeout pitch.

The pattern here is obvious — deGrom is throwing more of his strikeout pitches and less of his others, explaining the strikeout spike. But the change is curious. As deGrom struggled through injury in 2016, his velocity fell. A change in approach to mitigate the velocity loss would make sense in that season, but that did not occur, and he struggled to some degree in 2016 because of it. deGrom’s velocity is back to old form this season, but now he has strayed from the approach that made him so effective in 2015.

deGrom’s infatuation with the slider began during 2016, but he did not throw it nearly as often as he has this season. It was by far his most effective pitch last season. It was sort of his savior that year — his slider allowed a minuscule .168 average while his other four pitches were hit to a .276 average. deGrom clearly decided that his slider was his best weapon, and chose to make it a more prevalent pitch in 2017.

However, whether by design or mistake, with the increase in sliders, deGrom has also altered the location of his slider this season. (Comparisons will be made with 2015 season because of deGrom’s 2016 health). Here is a heat map of deGrom’s 2015 slider location. Pounded low and away from the arm side, like a typical slider. But now, take a look at the heat map of deGrom’s 2017 slider. It’s all over the zone, but placed particularly often at his arm side.

In 2015, deGrom had three primary offerings. The four-seam, the two-seam, and the slider. This is a heat map of his four-seam/slider combo in 2015, and this is the heat map of the 2015 two-seam. He attacked almost entirely glove side with the four-seam and slider, up with the slider and down with the two-seam. To counter, he pounded the extreme inside of the zone with the two-seam for a balanced offering. But look at the heat map of his 2017 four-seam/slider combo, his two primary offerings this season. deGrom is attacking across the entire zone with his two main pitches, but does not have that same vertical variance that he did previously. Instead of using the slider as an edge/out-of-the-zone wipeout pitch, he is trying to establish it as an in-the-zone pitch, but it has not been nearly as effective.

deGrom is attempting to attack the arm side with the slider instead of the two-seam, while also trying to attack the glove side with the slider to create balance in his approach. While it’s reaping benefits in terms of missing bats, it is not keeping hitters on their toes. Look at this table of deGrom’s slider profile:

Season K% SwStr% B% O-Swing%
2015 20.2% 11.8% 2.6% 36.1%
2017 40.0% 16.3% 8.9% 27.3%

One can see the massive spike in strikeouts and whiffs, which looks great. But people are also offering on the slider less because of the lack of deGrom’s balance with the two-seam, and it is leading to a lot more walks than in 2015. We see the exact same thing with the four-seam fastball:

Season K% SwStr% B% O-Swing%
2015 30.8% 11.5% 6.7% 31.8%
2016 35.6% 15.8% 16.4% 22.8%

The strikeouts are nice and all, but they are coming at a hefty cost in other areas. deGrom is not commanding the strike zone like he did previously. He has not lost his pitch control, as his Zone% in 2015 and 2017 are nearly identical, but he has lost some of his authority over hitters and is not manipulating them.

But it is not just the walks that have been more of a problem. In 2015, deGrom’s Hard% of 26.3% ranked 19th among qualifying starters. In 2017, he is sitting at just 69th out of 94 qualifiers with a 35.6% Hard%. Also, deGrom has given up six home runs in his last five starts. He gave up 15 in 30 starts in 2015.

This could all be an overreaction, of course. We are only seven starts into 2017, and deGrom could just be getting acclimated to his new approach. And it is not like deGrom has been getting walloped — he is pitching all right. However, this could also be an overreaction on deGrom’s part. With decreased stuff and velocity due to injury in 2016, deGrom saw a dip in his strikeouts from 2015. He may have lost confidence in his previous approach after his minor struggles last year, and has overcompensated in 2017 by trying to miss bats all the time. The new approach has not been quite effective this season, as deGrom has sacrificed command and soft contact to create more whiffs.

We hoped you liked reading Jacob deGrom’s Strikeout Spike by Henry Still!

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