In Praise of the Rich Hill Curveball

Journeyman Rich Hill has enjoyed a resurgence in recent years, thanks in large part to his devastating curveball. In honor of his free agency, let’s take a detailed look at one of the most versatile pitches in baseball.

For a marquee free agent, Rich Hill has had an atypical Major League career.  He’s bounced around the league since debuting for the Chicago Cubs in 2005, and he can proudly say he’s worn the jersey of eight Major League teams after getting traded to the Dodgers this past summer.  He’s had mixed results throughout his career, due in no small part to his inability to stay healthy.  Plagued with back, leg, shoulder, and elbow issues, Hill has spent a good part of the last decade on the disabled list.  The 37-year-old doesn’t have a particularly flashy or deep pitch arsenal like his former Dodger teammate Clayton Kershaw, and he averaged a pedestrian 90 mph on his fastball in 2016.

So, why then do we love watching Rich Hill pitch?  Well, first, he’s kind of nuts.  To say he wears his emotion on his sleeve is an understatement, and over the course of his summer with the Dodgers, he showed a propensity to scream and fist pump regardless of score or inning.   Indeed, he sometimes would celebrate so hard that I feared he might hurt himself.  Do you, Rich.


But there is a second reason Hill is amazing to watch: he’s the owner of a majestic curveball that often makes hitters look silly.  He throws the pitch from various arm angles, with fluctuating velocity and break, which makes it an exceedingly difficult pitch to hit with any success or regularity.   For example, check out these two Hill curveballs:



The top pitch is thrown at 64 mph from a high arm slot with a big break, and the bottom pitch is thrown nearly 10 mph harder from a sidearm delivery with sideways action.  Hill throws some type of curveball roughly 50% of the time (more than any other big league pitcher), and his ability to vary the speed and break of the pitch is a huge key to his success.

In honor of Rich Hill’s free agency, I thought it would be interesting to compare Mr. Hill’s breaker with the curveballs of the rest of the league.  Again, we turn to MLB’s PITCHf/x data for insights.

Rich Hill’s Curveball is Different

PITCHf/x tracked over 63,000 curveballs in 2016 (of which 1,007 were from Rich Hill), and the data gives us a wealth of information about the velocity, spin rate, break angle, and break length of those pitches (among many other variables).  For the purpose of this analysis, we isolated curveballs based on the “Pitch Type” classification contained in the raw data.  Generally, we should be wary of using the Pitch Type classification because the same pitch can often be classified a number of ways (e.g., curveballs and sliders are similar).  Yet, because PITCHf/x classified nearly all of Rich Hill’s 2016 breaking pitches as curveballs (rather than sliders or a mix of the two), we are confident that the Pitch Type classification will work for this analysis.

Anyway, let’s get to the fun stuff.  Below is a series of scatter plots which compare Rich Hill’s 2016 curveballs to the league average in terms of velocity, spin rate, break angle, and break length.  Some rather technical definitions are necessary before we proceed.  According to Mike Fast’s PITCHf/x glossary, break angle is the angle at which the ball breaks from the catchers perspective; the greater the number, the greater the horizontal break.  Break length is the largest deviation from a straight line between the pitchers release point and when the ball crosses home plate.  The actual numbers aren’t hugely important; just remember that all else equal, the greater the break angle and length, the more the pitch moves.

The red dots are Hill curveballs that were either (1) called a strike or (2) were swung at and missed by the batter.  Combined, these two defense-independent outcomes are my indicator of a successful Hill curveball.

One theme is apparent from the pictures: Rich Hill throws many different types of curveballs, evidenced by the fact that the pitches don’t heavily cluster around a particular velocity, spin rate, break angle, or break length.   You’ll also notice that Rich Hill throws his curveball slower than the average pitcher yet with a bigger break and much more spin.  The effect is a devastatingly big breaking ball that tumbles down on the hitter at the plate.

Which Hill Curveball is Most Successful?

The graphs above prove that Hill throws many different types of curveballs, and the red dots show that he has success — at times — with just about all of them.   But which type of Hill Hammer is successful most often?   To find out, I grouped each of Hill’s roughly 1,000 curveballs into velocity, spin rate, and break angle buckets, and then created heat maps showing the relative success of each.  As above, success is defined as those curveballs that were either called a strike or swung at and missed by the batter.  The top table shows the success percentage for a given bucket, and the bottom table shows the number of pitches thrown by Hill contained in that bucket.


You’ll see immediately that success (as we define it) is fairly spread out across the various  velocity and spin rate buckets.   That said, there are still some interesting takeaways.  Namely, Hill throws most of his curveballs between 73-75 mph, but he often has good success when he’s able to throw the pitch a bit harder.  Further, he threw a high portion of his pitches with a spin rate between 1,725 and 2,135 rpm, but he had above-average success when he was able to spin the ball either faster or slower than his normal curveball.   Granted, the number of pitches in these other buckets are small, but they provide interesting observations nonetheless.

Next, let’s take a look at spin rate and break angle.


Again, you’ll notice that success is not heavily clustered around a specific spin rate or break angle range.  That said, Hill throws the majority of his curveballs with a break angle between 11-15 degrees, but he also has a good success when he throws the pitch with shorter break (between 9 and 11 degrees) and with less spin than average.

Let’s look at our last combination, a heat map for velocity and break angle.


Once again, success percentage is fairly spread out across the buckets.  Yet as we saw above, Hill had good success in 2016 when he threw his breaking ball a bit harder than average and with a little less break than average (i.e., more like a slider than the big, looping curveball).   This suggests that Hill might benefit from throwing a harder, shorter-breaking version of the pitch more often.

The above is merely food for thought.  It is not, however, a call for Hill to alter his approach.   He is a master of varying speed and break, and his ability to adjust his curveball based on feel and the game situation is why he will soon sign a big (albeit short) contract.   Further, his ability to induce weak contact with his curveball is a huge piece of his success; that piece of his game is not captured by this analysis because I’ve chosen to focus only on those curveballs which were not put in play.  If anything, the above numbers indicate that Hill should continue to vary the look of his curveball as much as possible, since the data confirm that he can be successful across a very wide array of curveball types.

In other words, keep doing you, Rich.  I’ll be rooting for you.


Author: sittinglow80s

Former player, current student, curious fan

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