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The Curves of Zack Greinke

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Zack Greinke earned the 2009 Cy Young Award earlier today. It was well deserved, and not much of a surprise. I've covered Greinke via PITCHf/x on a few occasions* (here, here, here, here and here), so I'm taking this opportunity to look at Greinke's curveball -- which is thrown at a wide range of speeds.

*If you check out those links, you'll see some flight paths, learn about his sinker, compare his

fastball locations to Rich Harden's and explore head-to-head match-ups against Kevin Milwood and John Lackey.

Greinke's best pitch is his slider. It's one of the best pitches in baseball, and he complements it with two above average fastballs (four- and two-seam varieties), a change-up and the aforementioned curveballs. For starters, Greinke can vary his pitch speeds by nearly 40 mph -- high 90s fastball and a low 60s curveball.

But Greinke's curve is thrown anywhere from the lower 60s up to the lower 80s.

Greinke's average curveball is around 75 mph. I split them into three groups, making the cut-offs at 72 and 78 mph. Before doing that, I classified all of his pitches (7512 going back to 2007). It was important to keep the curves and sliders apart, especially at their respective upper and lower speed ranges. I can't say I'm 100% accurate in my splitting of pitches, but I'm more than satisfied with the results.*

*mostly manual folks, it's hard to automate the classification of pitches that are that close together. Not that "we" aren't trying.

Here's where I ended up with Mr. AL Cy Young 2009's curveball.


speed # MPH
fast 128 82.8
regular 235 74.9
slow 154 68.6
517 75.0


Good mix. Obviously, we've wandered into the land of small sample sizes. Put on your error bar goggles.

speed In Wide Zone
B:CS Swing Chase Watch
fast .445 2.9 .563 .437 .281
regular .604 1.0 .319 .194 .585
slow .571 1.6 .448 .303 .432
.555 1.4 .418 .300 .477


Unless he's putting something extra on it, it's a strike. Well, it's a strike for more often than the average pitch (.53).

The relative wildness (for lack of a better term) on the faster variety serves a purpose. It gets more swings, especially out of the zone, than the slower varieties.

Opponents rarely seemed to swing at the main group of curves, taking a lot of strikes (nearly 6 of 10).

There is a difference already, with the slow group actually sitting in between the fast and regular in all the categories above. But now things start to change.


speed Whiff
fast 0.375
regular 0.173
slow 0.348


The changes in speed seem to help. Remember, both the fast and slow are chased out of the zone more often, which helps those whiff rates.

Hitters do make contact, quite often, and here's what happens.


speed GB% FB% PU% LD% HR/FL%
fast 50% 25% 0% 25% 17%
regular 49% 29% 3% 20% 6%
slow 32% 35% 10% 23% 0%
43% 30% 4% 22% 6%


HR/FL is home runs per fly ball + line drive (average is around 7%, your park may vary).

I love ground balls as much (if not more) than most baseball fans, but I'll take the slow curve. Pop-ups are almost automatic outs. And in the off chance that home run rate is not a fluke....

The last measure are the run values. rv100 is runs allowed per 100 pitches relative to the league (MLB 2007-9) average. Negative numbers are better for pitchers. rv100E is the same thing, but batted ball outcomes (hits and outs, homers and singles) are discarded and league average rates for batted ball type (grounder, liner) are used instead. In other words, a ground ball is 3 parts out an 1 part single*, no matter what actually happened.

*not exactly, but you get my point

speed rv100 rv100E
fast -0.93 -1.85
regular -0.11 -0.55
slow -0.48 0.30
-0.43 -0.62


Go figure. Fast wins, both ways.

In case you're wondering, Greinke's 2009 slider had a rv100 of -3.18 and a rv100E of -2.72.

Greinke's favorite time to throw the slow curve was when he was ahead of right-handed batters. In 0-1, 1-2 and 0-2 counts, it was his choice just under 10% of the time. On 0-0 counts against, it checked in close to 9%, and wasn't used in any other situation more than 5%. The most common usage against lefties was, again, when he was ahead, but just over 4% of those situations saw the slow curve. He did not throw the slow curve, except for rare occasions, when behind in the count.

The fast curve was most frequently used when ahead or even, against both lefties and righties. In those counts, it was around 7-8%. Again, it was least likely to b used when behind.

Helping push first pitch curves to righties to nearly 1 in 4, Greinke used the regular speed curve was on nearly 15% of first pitches against right-handed batters in 2009. He was willing to use the regular curve when behind in the count (perhaps aware of the accuracy and Watch rate). Still, when he chose to throw a curveball when ahead, it was usually fast or slow.