Curveballs: Pitching vs Hitting Improvement

Curveballs. A well thrown curve can the the toughest pitch in baseball to hit.  Up until a couple seasons ago it was seen as an “out” pitch and that would be the only situation to throw it.  Now guys like Rich Hill have made a living by throwing the pitch as a primary.  If the pitch gets results why throw it on just certain counts? Certain batters have an eye for curves and can either hold off on one in the dirt or take a hanger over the fence.  It is tough to find a young ballplayer to can recognize a curve consistently enough and find success.  In this post we will look into the pitchers who improved their curveballs the most as well as the hitters who improved in their approach to curveballs.


Most every pitcher in baseball throws a curve, however there are only a handful that will rely on it.  We will look at those who throw curves as either their primary or secondary pitch.  Using BaseballSavant with a minimum of 100 results I searched up opponent batting stats for 2017 and 2018.  The guys with results in both seasons are the following:

These are the ones that for 2 years have thrown curveballs as a consistent weapon in their repertoire.  Guys like Kluber, Verlander, and Strasburg stick out as successful curveball throwers.  Other guys may be ones you done think of.  Now below you will find the difference of various categories from 2018 to 2017 (Green indicates most improved and red indicates worse performance):

Verlander was clearly the most improved from 2017 where he also had a very successful season.  Kluber had a ridiculous 2017 where he only allowed a .099 batting average against curveballs with a whiff rate of 52%.  This year he really let himself go posting a .104 opponent batting average.  Verlander went from a .234 opponent batting average to a .137 opponent batting average in 2018.  Of those who threw enough curveballs over the course of the past 2 seasons he was the most improved in many aspects of his curveball.  This is surprising considering he was really good in 2017.


Of all batters in baseball, who made the biggest jump from 2017 to 2018 in terms of hitting curveballs?  While Miguel Andujar would not be in this since he was not up in 2017, I want to note that he hit .410 against curveballs this season as a rookie.  Anyway, here are the 4 most improved hitters based on batting average:

J.D. Martinez was far and away the most improved based on this.  Here are some other interesting ranks:

J.D. is also the most improved based on WOBA.  His overall approach to curveballs improved making him the steal of the 2018 free agent class.  Some surprises in the other ranks.  Some free swingers in Carlos Gomez and Joc Peterson appeared to have been much improved in terms of whiff percentage in 2018.  Also it is encouraging the Harper was improved in whiff percentage in 2018 considering he had a “down” year.  The exit velocity rank shows Dee Gordon at the top.  He hit curveballs on average 13.4 mph harder than in 2017.  This is surprising considering the season he had in 2018.

Batter vs Pitcher:

So it turns out that the most improved in pitching curveballs and hitting curveballs are two superstars.  How did they do against each other this season?  J.D. went 2-3 with 2 singles, 2 RBIs, and a strikeout.

Curveballs have become such a big part of the game.  A nasty curveball can carry a pitcher to the top.  A hitter who can manage an at bat with a multitude of curves is very valuable.  Young players such as Bregman and Andujar have demonstrated they can hit the curve.  This is part of the reason they could be regulars in All Star games and MVP voting.


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