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First and worst: Curveballs of 2013

More fun with z-scores, as the best and worst pitch of 2013 series rolls on. Now, we turn our attention to curveballs.


The hook. A bender, Uncle Charlie. What got Barry Zito a lot of money. Whatever you call it, the curveball, in the proper hands, is a devastating pitch and a great equalizer for a pitcher who can master the quirks of the offspeed pitch. While not a dominating pitch, per se, like a fastball, the curveball can be a power pitch much like a heater for those who can throw it with enough velocity and snap to not only miss bats, but make knees buckle.

So who has a good 12-6 breaker? Or even an 11-5?

I am sure most of you know the drill by now, but to quickly recap, we will use FanGraphs data on curveball pitch type linear weights (CU/C) as well as vertical movement (CU-X), and horizontal movement (CU-Z) data to create a z-score for each in order to compare the variables to one another. A summary score (SUM_z) will then be calculated to give a final, single value for measuring the value of a given pitcher's curveball. The ten percent criteria will also be used, with only pitchers who used the pitch at least ten percent of their pitches being considered for our best/worst list. We will also break down our results by starters and relievers.

Thus far, we've figured out who has the best and worst changeups, four seam fastballs and sliders -- whose Jose Cuervo reigns supreme?

Name SUM_z Pct Use wOBA Against
SP, First Stephen Strasburg 4.89 22.8 0.150
SP, Worst Eric Stults -5.57 11.4 0.375
RP, First Jamey Wright 3.88 24.8 0.150
RP, Worst Cesar Ramos -1.96 10.8 0.274

...and once again, we find old friends from previous first/worst entries -- Jamey Wright and Cesar Ramos. We also find a somewhat mild surprise at the top of the starter list in Strasburg; I will leave it to you, gentle reader, to google some of Strasburg's exploits with the curve to confirm he is a deserving winner here, but suffice it to say, I was mildly surprised that neither Adam Wainwright's or Clayton Kershaw's bender made the top of the list. For those curious, Waino's curve ranked 3rd with a 4.06 SUM_z, while Kershaw's came in at number 22, with a 1.42 SUM_z.

Let's take a look at those composite z-scores for our quartet here for a moment, so we can see where strengths and weaknesses lie for each:

Name vCU_z CU-X_z CU-Z_z wCU/C_z
Stephen Strasburg 1.047 1.200 1.039 1.608
Eric Stults -3.135 -1.578 0.445 -1.301
Jamey Wright -0.346 2.625 1.284 0.319
Cesar Ramos -2.368 -0.618 1.401 -0.373

Overall, we find that each of the four does a good job of creating movement on their curveball in the z-plane, while Strasburg sets himself apart from the other three with his above average velocity on his breaker -- this isn't terribly shocking if you have seen his curveball, as it is truly a power pitch. However, this velocity comparison is only against other curveballs, not each pitcher's fastball, like what we saw with changeups. While change of speed is always an important and valuable talent, I did not feel that it has as much weighting on how good a curveball is as compared to a changeup, hence the standard approach to handling pitch velocity -- a direct comparison versus one that is predicated upon the difference in velocity between it and another pitch.

With that said, what else plays a role in having a good curveball? Two other factors that potentially play a role could include release point -- does it come out of the pitcher's hand the same way and in the same location as his fastball -- and also arm speed -- is the pitcher slowing down his mechanics and arm in order to get on top of the pitch to ensure a good snap on his curve. The latter we don't have data for, but release points we can look at, with the help of Brooks Baseball. From there, we can grab the horizontal (CU, H) and vertical (CU, V) release point values for our quartet, along with the same data for their fastballs ('FA, H' and 'FA, V', respectively), and compare them to see how close they are to one another. In order to compare a two dimensional value in one dimension, I have multiplied the horizontal and vertical values of each for each pitcher, giving us FA_h*v and CU_h*v values. From there we subtract those two values and take the absolute difference (Abs Diff) to give us a general idea of how close each pitcher's curveball's release point is in comparison to their fastball.

So what does that look like?

Name FA, H FA, V CU, H CU, V FA_h*v CU_h*v Abs Diff
Stephen Strasburg -1.34 6.21 -1.32 6.20 -8.321 -8.184 0.1374
Eric Stults 1.46 6.51 1.68 6.69 9.505 11.239 1.7346
Jamey Wright -2.78 6.47 -2.9 6.50 -17.987 -18.850 0.8634
Cesar Ramos 2.15 6.49 2.14 6.49 13.954 13.889 0.0649

Not surprisingly, Strasburg's curveball is coming out of his hand is just about the same place as his fastball in average in 2013 and is much better than compared to Eric Stults. However, our worst curveball 'winner', Cesar Ramos, does an even better job than Stras in making his curveball come out of the same arm slot (for the most part).

So what does that tell us?

One thing comes to mind immediately. Perhaps it's arm speed that is playing a larger role in the overall success of the curveball for guys like Strasburg and Jamey Wright more so than raw velocity or arm slot. Sadly, we don't have data on arm speed, so we are left to make thoughtful guesses as to its true value when discussing a good curveball. Much like what we saw with changeups, we again see some fickleness in our results and reality; even the 'bad' offerings, when looking at wOBA against, are effective pitches. As such, it might be that for some pitchers, their pitches derive their value not so much from how good they are as standalone pitches, but how different they might be from their other offerings; sometimes, a pitch can be good more for what it isn't than for what it is.


All data courtesy of FanGraphs and Brooks Baseball.

Stuart Wallace is an associate managing editor and writer at Beyond The Box Score. You can follow him on Twitter at @TClippardsSpecs.