Sabermetrics

A Godley Curveball

Who has the best pitch in baseball? If we polled a thousand people in the baseball industry, we would hear a lot of different answers. Some would say Corey Kluber’s breaking ball, others would say Zach Britton’s two-seam sinker or Aroldis Chapman’s record-setting fastball. One could make the case that Clayton Kershaw has two pitches that could be in this discussion. Nobody, however, would even think to mention Zack Godley. Heck, before last season, most people probably hadn’t even heard his name. A year later, there is a case to be made that his curveball was the best pitch in all of baseball in 2017.

Coming into the 2017 campaign, Godley had never started more than 12 games or thrown more than 75.1 innings at any level. He was thought of as nothing more than rotation depth, a guy that could make a spot start before being sent back down to the minors. Godley not only proved his doubters wrong last season, he quietly emerged as one of the top starting pitchers in all of baseball. Despite never having more than a half-season’s worth of starts, Godley threw 155 innings in 25 starts for the D’Backs en route to the 17th highest WAR amongst all MLB starting pitchers, tied with Michael Fulmer and ahead of Cardinal’s ace Carlos Martinez.

When a player comes out of nowhere, it is often the result of good fortune and peripheral statistics that suggest extreme regression for the following season. This is not the case for Godley, however, as the young D’Backs starter was 14th in the MLB in xFIP thanks to a top 10 groundball rate and a lethal curveball that routinely flummoxed opposing hitters.

According to Fangraphs pitch values, which measures the effectiveness of each pitch on a per-pitch basis, Godley’s curveball was the 8th most valuable pitch in baseball in 2017

Below is a list of the pitches that ranked higher:

Player Pitch Type Pitch Value (w/pitch/C)
Clayton Kershaw Changeup 6.47 wCH/C
Corey Kluber Breaking Ball & Changeup 4.68 wCB/C & 3.48 wCH/C
Carlos Carrasco Changeup 3.58 wCH/C
Max Scherzer Slider 3.33 wSL/C
Zack Greinke Changeup 3.48 wCH/C
Alex Wood Changeup 2.58 wCH/C
Zack Godley Curveball 2.40 wCB/C

On a per-pitch basis, all of these pitches were tremendous in 2017, but a weapon is only as lethal as the frequency with which it is deployed. That being said, let’s take a look at how often each of these pitches was utilized.

Zack Godley Curveball 35.6%
Max Scherzer Slider 28.9%
Corey Kluber Breaking Ball 27.4%
Alex Wood Changeup 25.4%
Carlos Carrasco Changeup 16.5%
Zack Greinke Changeup 15.7%
Corey Kluber Changeup 6.5%
Clayton Kershaw Changeup 1.7%

Out of the most effective seven pitches in the MLB last season, Godley threw his curveball over 20% more than the next closest pitch. It can be argued that since Kluber has two of the best pitches in the game, he doesn’t have to be as reliant on any one pitch, which is true, but this article is arguing what the single best pitch is, not who the single best pitcher is.

Any opposing hitter that reads scouting reports or watches video was fully aware that they would see Godley’s curveball at least once in every at-bat, but he was still able to generate a swing-and-miss 21.7% the time. He was also able to get hitters to offer at his curveball out of the zone more than half the time as his bender produced an O-Swing% of 50.3%.

When hitters were able to make contact on Godley’s curveball, they didn’t have much success. In fact, out of all the batted balls against the pitch, 76.8% of them were either ground balls (57.8%) or infield pop-ups (19.0%). In other words, when hitters weren’t completely whiffing on Godley’s curveball, they were generating weak contact. According to Statcast, hitters expected wOBA was just .222 off of Godley’s curve.

While many right-handed pitchers use their breaking balls primarily against right-handed hitters, while trying to get lefties out with some variation of a changeup, Godley proved that his curveball could baffle hitters regardless of their handedness.

Batter Handedness Curveball Pitch Usage wOBA Against
Against RHH 34.08% .217
Against LHH 36.78% .196

While conventional wisdom would suggest that Godley throw more curves against righties, he actually threw it slightly more against lefties and had marginally better results. Part of having a dominant pitch is having the confidence to throw it regardless of who steps to the plate. In 2017, Godley did exactly that and watched while hitters consistently walked away frustrated.

While Godley was capable of throwing his curveball against hitters from both sides of the plate, his secret to success rests in his command of the pitch. The following two heat maps illustrate this:

Curveball Location Against Right-Handed Hitters (Catcher’s perspective):

Godley Curveball v: RHH.png
As you can see, Godley consistently painted the low-and-outside corner to righties, a location that any right-handed hitter can tell you is extremely difficult to hit. Not only did he throw enough strikes with this pitch to get his fair share of called strike threes, he also made sure that when he did miss his desired location, it was out of the zone where hitters were unable to drive the ball.

Next, let’s look at where he threw his curveball against left-handed hitters:

Curveball Location Against Left-Handed Hitters (Catcher’s perspective):
Godley CB v:LHH.png
While Godley caught a little more plate when he threw his curveball against lefties, his ability to throw the pitch down and away with consistency made it extremely effective.

Godley not only dominated both sides of the plate with his curveball, he also had the boldness to throw it in any count. As with any pitcher who has a dominant pitch, Godley leaned on his curveball to punch out hitters with two strikes. Out of his 155 strikeouts, he recorded 111 of them by virtue of his curveball, by far the highest percentage in the MLB.

However, his curveball was far more than just an out-pitch to Godley. In fact, the D’backs righty was the only starting pitcher to throw his curveball more than 200 times last season when he was behind in the count. The ability to pitch backward is a skill that all pitching coaches drool over because it makes pitchers less predictable and as a result, less vulnerable to hitter’s counts. When a hitter is 1-0, 2-0, or 3-1, they typically sit on a fastball that they can drive, and in most cases, they get it. With Godley, however, hitters have to stay on their toes, allowing him to maintain an advantage regardless of the count.

Even when opposing batters worked the count full on Godley, they were still unable to sit on a fastball. In fact, Godley was the only pitcher in the Statcast era to throw his curveball more than half the time (53.2%) in full counts.

Here is a look at Godley punching out fellow breakout star Tommy Pham on a 3-2 curveball:


So by now you probably get the point. Godley has a pretty awesome curveball no matter how you slice it. But what is it exactly that makes this pitch so special?

The easy answer is that Godley throws his curveball extremely hard. Out of all pitchers (including relievers), Godley’s curveball recorded the 5th highest velocity in the MLB, coming in at an average of 83.4 mph.

The difference between Godley and the four guys who throw harder curveballs is that he is the only one whose fastball averages less than 93 mph. As a result of Godley’s fastball clocking in at 91.9 mph, the differential between the average speed of his curveball and the average speed of his curveball are much more narrow.

On the surface it may seem like this would be a disadvantage, but because Godley’s fastball and curveball look so much alike, hitters are routinely thrown off at the last second when they are gearing up for a heater and it suddenly falls off a table.

Additionally, out of the 20 hardest curveballs in the league last season, Godley throws by far the lowest rate of fastballs at just 32.9%. In fact, besides Lance McCullers — who is the next closest in terms of low fastball usage at 40.4% — the average fastball usage among this group is 52.9%. That is a full 20% higher than Godley.

This matters because while hitters can guess fastball and be correct roughly two-thirds of the time against other pitchers, they would be guessing incorrectly over half the time against Godley. Similar to the point I made earlier about Godley’s willingness to throw his curve in any count, his rare pitch usage numbers make him one of the more unpredictable starting pitchers in baseball.

Just for fun, here is another look at Godley using his curveball to strike out one of the game’s best hitters:


 

 

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About Traven Tapson

I am a recent graduate from Claremont McKenna College pursuing a career in baseball operations for an MLB team. I am fascinated by the analytical side of baseball and use this blog as a platform to share my insights and knowledge with those who share my curiosities.
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