Jake Arrieta is Adjusting his Pitch Selection, and It’s Working

In the height of his dominance that came two seasons ago, Jake Arrieta used his sinker and his famed slider/cutter hybrid to leave opposing hitters helpless. And after the slightly-awry season that followed his Cy Young brilliance, Arrieta seems in the early going this year to have found a couple of ways to right his ship.

It’s well known that Jake Arrieta is not throwing as hard this season, and if he is doing it to improve his command, the results indicate that it appears to be working so far.

But not only that, Jake Arrieta has also been doing something else of late that has not been quite in keeping with what he has done in the past two seasons, and that has been a shift in how he approaches hitters to compensate for the decline in the effectiveness of the out pitch he relied on so heavily during his Cy Young season.

Since 2015, Arrieta has moved away from his sinker and has shown a greater reliance on his curveball. And that slider/cutter hybrid that he leaned on so successfully in 2015? Its usage dipped 11 percent last season and has dropped another 3 percent in this one.

Here’s a simpler look:

Fastball Sinker Change Slider Curve
2015 7.43% 43.63% 4.46% 29.52% 14.97%
2016 5.26% 59.71% 4.15% 18.74% 12.13%
2017 7.80% 51.77% 7.33% 16.55% 16.55%

While some of the changes in those numbers are negligible, the fact that Arrieta is now using his curveball as often as he does his former out pitch is telling in a few ways. Data from Brooks Baseball is, of course, incomplete from his first start of the season on April 4, but of the tallies that are available, he went to the curveball nearly twice as much and almost as often as his sinker in that outing, and on two occasions he has used his curve more often than his slider.

To be clear, this pitch is probably not a suitable replacement for the slider that Arrieta found such success with in his Cy Young season, but it has potential to support his other pitches when used more often than he has in the past.

In fact, his curve was ranked as the third best of National League pitchers who threw it in 2016, and it generated a 17.2 percent swing-and-miss rate last year, behind only Jose Fernandez and Madison Bumgarner on that list.

It’s a quality pitch, and while he has already used it more often than he did last year, it is still one that Arrieta could stand to offer up with even more regularity than he already has. This is not to suggest yet that the now relatively sparsely used slider has a replacement, however. His primary two-strike pitch is still his sinker, but Arrieta is not throwing his curve in one place that he might be well-served to do so, and that is when the batter gets ahead.

In these hitter-friendly counts—which Arrieta was especially prone to put himself into last season—he almost never uses it. When the batter is a lefty, he will use the curve just 16 percent of the time, and when the batter is right-handed and ahead in the count, he just doesn’t use his curve at all.

This last part is understandable, as right-handed hitters hit their home runs on his curveball more than any other pitch, and they swing and miss at it under eight percent of the time. Against lefties, however, things change significantly. Thus far in 2017, no one has tagged him for a home run on that pitch from that side of the plate, and the swing-and-miss rate on his curve goes all the way up to just a hair under 14 percent. They’re less apt to swing at it, but what is interesting is the difference in how often he throws the pitch for a strike.

Curveball LHH RHH
Thrown for a strike 44.19% 59.26%
Thrown for a ball 44.19% 11.11%

Arrieta is hitting the zone with a much higher level of consistency to right-handed batters, and he rarely misses with the curveball to righties, either. All told, it can be a very effective pitch, but much more so to lefties.

A funny thing, though, about that slider is the effect it still has on the guys hitting from the other side of the plate. Where the curveball probably cannot be relied upon here, his slider still can. Even thrown at a slightly diminished speed from the pitch’s heyday in the dog days of 2015, he continues to get something out of it.

Where the lefthanders feast on the pitch to the tune of a .714 ISO, their counterparts can’t quite make sense of it. Of the 43 times Arrieta has thrown his slider to right-handed batsmen, they’ve managed a hit just twice (yes, one of those was a home run, but let’s focus on the good here).

In short, right-handed hitters love his curve and hate his slider, and lefties are the opposite. But that is probably omitting just how much left-handed batters hate his curve. Of the 43 times he has thrown that pitch to hitters on the left side, they have not hit it at all.

This is a big change from how he approached batters two seasons ago. In 2015, he threw the slider at them almost indiscriminately, and they were almost equally unable to do anything other than flail at it impotently. By now, Arrieta knows that this pitch does not do what it did then, and he has adjusted. Last year’s results were middling, but so far this season, he has asserted himself as at least the second-best starter in the rotation (sorry, Kyle).

Taking this a step further, and acknowledging the sample size with a sigh and an almost imperceptible eye roll, Arrieta has actually been better in some ways so far this season than he was when he was a Cy Young pitcher.

In 2015, he posted an overall K/9 rate of 9.28 and a BB/9 of 1.89. This year, so far at least, his K/9 is 10.58 and his BB/9 is 1.82. Just the walk rate alone is enough to declare Arrieta cured of what ailed him last season, as it has been cut almost in half thus far.

Whether these numbers will hold will take time to tell, naturally, but they are encouraging. Just a few months ago, I asserted that extending Arrieta beyond this season was a bad deal, but he is giving me some reason to reconsider. As he has modified his approach, not just in how he decides what to throw to the batters he faces, but also in how hard he throws the ball, Arrieta is showing a side of himself that is prepared to adapt and find new ways to thrive, and I am inclined to bet on that.

Lead photo courtesy David Kohl—USA Today Sports

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2 comments on “Jake Arrieta is Adjusting his Pitch Selection, and It’s Working”


I just see statistical noise, esp. wrt 2017.

Very interesting. It will be especially interesting to see how this looks a month from now. I’m as unsophisticated as they come in measuring such things, but he LOOKS like a different pitcher from the 2nd half of last year.

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