Chris Perez - Fastball Release Points

Not too long ago, Chuck took a look at something I did on Chris Perez over at Beyond the Boxscore.  You can find Chuck's post here, along with links to a couple things at BtB.  This about sums it up:

There’s clearly a difference between how Perez performed when there was less than 2 inches difference between his fastball delivery and his slider delivery and when there were 2 or more inches difference between the 2 deliveries.....When he was more consistent w/ his 2 release points, he was much better

By "better", Chuck meant this

This raised a bunch of questions, and this is just a look at a couple of them, posed in the comments by fourstick:

whether there’s a difference in velocity between the overhand fastball he throws to righties and the 3/4 fastball he throws to lefties.

whether that velocity is offset by better overall movement.

more effective pitcher throwing 93-94 from 3/4 with good movement than throwing 96-97 from over the top with less movement, especially considering that the arm slot would be the same as his slider.

I could think of two ways to approach the questions, in terms of splitting the data into groups, at the most basic level.

1. lefty/right split (ignore arm angle)
2. arm angle split (ignore batter hand)

Getting the first one out of the way, I'm seeing no real difference between fastballs to lefties and righties for Perez, on any PITCHf/x dimension.  For this bit, I only used his home games.

Clockwise from the top left, that's speed at release (55 ft. from home), lateral "spin movement" in inches (negative is to the catcher's left), release point - feet from the middle of the rubber, then bottom-right is release point height, also in feet, vertical spin movement and finally speed at home plate.

The rest of this is going to focus on one thing - movement, but also release point/angle.  And plate location.  So three things.  But in one picture. 

Here are two versions of that one picture.  Confused yet?  I'll explain.

Starting from the beginning ... I took all of Perez's PITCHf/x data, and found the average release points for every game he appeared in.  I did not include curveballs, since he throws those more over the top. 

Once I had the average point for each game (yes, this is a crude approach, it gets cruder) I categorized each pitch as a "high", "middle" or "low" release.  The first pass took anything that was above average on both x0 and z0 and called it a high, pitches that were both below were low and the rest middle.  The second (better) pass only took pitches outside of 1 SD in both dimensions.

The first pass, shown in the top flight path, treats a lot of potential low angle pitches as middle.  The second pass may still not be alright, but I'm not going through every game visually (thank you PERL + MySQL).

No matter how I sliced it, by batter hand or by either release point split, the fastball was always a shade over 96 mph.  It does not appear that Perez loses or gains any velocity when he changes his arm angle.

Movement, that's another story.  There is a difference - maybe a half inch of tail and as much as an inch and a half of sink.  The dropping of the arm does change the spin axis enough to make a difference, but I really think the biggest impact is not the spin, but the initial trajectory and the resulting plate location.

Here are plate locations by release point group (High is blue, Low is red).  Same deal as before, first pass and second pass.

Even though the data took us away from fourstick's original questions - the speed difference wasn't there - there clearly is a big difference when Perez drops his arm on the fastball.  The good news is, most of those are against lefties, otherwise he'd be filling up the trainer's room.

Using the second pass, since the groups are more distinct, small sample sizes and everything, here's more than you need to know* about High Middle Low and Chris Perez.  I so totally lied when I said this would only be about 1 2 3 things.

*that's another lie.  There's more.

You could argue - maybe - there's a slight loss of velocity when he's out of slot high or low. 

Outcomes.  Since you may not be familiar with my schtick, here are some quick definitions. Quick if read by the guy from the old Fed Ex ads. 

Swing = swings/pitches; Whiff = misses/swings; B:CS is as called by the ump on takes only; IWZ is pitches in the "wide zone" - a full two feet wide and within the average Gameday operator set values for each hitter aggregated across all pitches seen by that hitter; Chase is Swing rate again, but out of the wide zone; Watch is take rate (1 - swing rate) in the zone; nkSLG is total bases on balls fair in play divided by balls fair in play; TBP is total bases divided by all pitches.

First and foremost, no one has a hit off the low arm slot fastballs.  The drop-off in swing rate isn't that bad - just 2 less swings over 50 pitches - despite the failure to hit the zone.  I wonder, when he drops down, if hitters think "slider" and then the ball comes out 96 mph tailing and sinking.  So, while this may have gone away from the notion of speed vs. movement, I remind you of one of the comments by fourstick about the low arm slot possibly being to Perez's advantage:

especially considering that the arm slot would be the same as his slider.

The data is hanging out waiting to be asked more questions.  Fire away.