DeSclafani Spins His Way to a Victory

Last night Anthony DeSclafani threw a four hit shutout against the Arizona Diamondbacks. Normally this wouldn’t catch my attention, but it did because of the disappointing performance DeSclafani had in his last outing against the Los Angeles Dodgers.

Against the Dodgers on August 21st DeSclafani went 7 IP, 8 Hs, 1 BB, 6 Ks and 4 ERs. Not a bad start but against a better offense in the Diamondbacks last night he went 9 IP, 4 Hs, 1 BB, 9 Ks and 0 ERs, a remarkable start for any pitcher and especially for DeSclafani. After seeing last night’s results, I dug deeper in to the data to see what I could find that was different.

Before I get in to that let me say how wonderful it is to have the data we have from games these days. Within minutes of a game being finalized anyone can look up how many of each pitch a pitcher threw, what the velocity of those pitches were, how many were strikes versus balls and a host of other information. One of my favorite sites for this data is BrooksBaseball.net and that is where I did the bulk of my research for this post.

After looking over the pitch data from the two games in question one big difference jumped out at me. That difference was the amount of rotations DeSclafani was getting on his pitches in last night’s start compared to the August 21st start. Below are charts that show the RPMs of his pitches from both the August 21st and 27th starts.

Data and charts courtesy of BrooksBaseball.net

As you can see from the charts not one pitch had an RPM level of 2400 or above on the 21st, while several pitches on the 27th had over 2500 RPM. What does that mean though?

In very simple terms an extreme spin rate, one way or the other, equates to a harder pitch to hit. The average major league fastball has a spin rate of between 2,000 and 2,200 RPM. Major league hitters see that spin rate and are able to track where that pitch will end up crossing the plate easily because they see it so often. However, if a pitcher has an extremely high spin rate, or extremely low, the ball acts differently from what the hitter is use to seeing. In the case of a high spin rate a fastball tends to stay higher in the zone for a longer period of time. If a pitcher has a below average spin rate, Dallas Keuchel for example, then the ball drops out of the zone sooner than a hitter is use to. Either way a fastball is harder to hit if it doesn’t end up in the strike zone where the hitter is use to it being. A breaking pitch, such as a curve or slider, that spins faster will have more vertical and horizontal movement. Again, making it much harder to hit.

In DeSclafani’s case you can see that his pitches on the 21st had an average to below average spin rate leading to less horizontal and vertical movement on his pitches. On the 27th his spin rate was above average and lead to more vertical and horizontal movement on his pitches. A perfect example is the movement on his slider. Against the Dodgers his slider had a horizontal break of 2.54 and a vertical break of 0.37, whereas against the Diamondbacks the same pitch had a horizontal break of 2.83 and vertical break of 1.72. It is easy to see that the faster a ball rotates the more movement it will have and therefore the harder it would be to hit. Because we know this now we better understand why the outcome of last night’s game was so much better than the August 21st game.

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