# The Hardball Times

## All about the high inside fastball

by Nick Steiner
November 13, 2009

### What exactly is a high inside fastball?

"Well, duh, Nick. A high inside fastball is a pitch that is high and... wait for it... inside, hence the name. You don't seem to be very sharp, I think I'm going to stop reading now."

While the question may seem stupid, it's necessary to define the pitch so we can take a look at it in more detail. For one, I'm interested in looking at pitches in the high inside corner of the strike zone, not ones that are actually high and inside. The reason for this? I don't know, it seemed more interesting to me. Anyway, using the called strike zone coordinates for left-handed and right-handed hitters that John Walsh found here, I divided the zone into nine equal parts.

For a RHH, a high inside fastball is between -.333 and -1 feet from the center of the plate, and between 2.93 and 3.5 feet above the ground; and for a LHH, it's between .125 and .825 feet from the center of the plate, and between 2.86 and 3.4 feet above the ground. I included all four-seam, two-seam and "normal" fastballs, mainly to get a bigger sample size, but I excluded sinkers and cutters.

### Okay, so why should we care about them?

Well, for one, they are really freaking good. Using the methodology detailed by Walsh, I calculated the run value per 100 pitches for all high inside fastballs from 2007-2009:
`Numberrv100RHP to RHH16518-3.03RHP to LHH13166-2.73LHP to RHH8514-2.21LHP to LHP4145-2.75`
These are from the pitcher's perspective, so the lower the number the better. For reference, the best fastball in baseball this year among qualifiers belongs to Chris Carpenter at 2.01 runs better than average. So simply throwing a fastball on the high inside corner turns an average fastball into the best in baseball!

Actually, it's not quite that simple. Pitchers who have the guts and the command to challenge batters up and in are generally very good pitchers, so the run values of the high inside fastball may be inflated due to selection bias. So I subtracted the rv100 of each pitcher's fastball that was thrown up and in by the overall run value of the fastball. I got a weighted rv100 of -2.34, so it appears that there is no bias.

### How much does speed matter?

Pitch speed is obviously one of the most important facets of pitching. In most situations, you would always prefer the guy with the 98 mph fastball to the guy with the 88 mph one. However, when going up and in, does it make that much of a difference? If Joel Zumaya goes up and in with his triple-digit heater, is it going to be better than J.P. Howell's 87 mph junk? To answer that I looked at the rv100 for six different speed groupings, and split it up by batter and pitcher hand:
`SpeedRHP to RHHRHP to LHHLHP to RHHLHP to LHHAverage<870.84-1.94-0.75-1.91-0.8387-89-3.92-2.40-1.73-1.09-2.4789-91-2.72-2.96-2.51-2.74-2.7491-93-2.71-2.62-1.84-3.56-2.5993-95-3.94-3.53-4.60-2.76-3.8195-97-3.21-2.70-2.61-5.68-3.06>97-3.76-2.52**-3.13`
*Too small of a sample size

It's a little hard to make sense of those data. When you take the averages, the effectiveness of a high inside fastball rises from a little bit better than average when it's thrown below 87 mph and peaks from 93-95 mph, and then drops but plateaus at an above-average rate for the next speed groupings. However, when you compare each subgroup (batter and pitcher handedness) to themselves, it isn't so clear.

For example, from a RHP to a RHH, an 88 mph fastball up and in is just as effective as a 94 mph fastball, and more effective than pitches thrown harder than that. That comes in a very big sample size as well, more than 1,700 pitches for each group, so you can't just chalk it up to random variation. That effect is also present on fastballs to a LHH from a RHP. Although the the rv100 dips from 93-95 mph, the rest of the groupings are virtually indistinguishable from each other.

Another interesting nugget is that the high inside fastball from a LHP to a LHH that's at least 95 mph is nearly six runs better than average per 100 pitches. The main reason for that is there have been only 121 such pitches over the past three years. Three years! Even if there were something extra special about that pitch, you can't tell from the actual data.

So we've found that pitch speed has a detectable, but sporadic, impact on the effectiveness of the high inside fastball, but what about pitch sequencing? Is a high inside fastball better when thrown following a fastball or an off-speed pitch, and perhaps more interestingly, how does a high inside fastball impact the pitch that follows it?

Let's check out the first question first. Sorting by batter and pitcher handedness, here is how much the high inside fastball is improved on based on the previous pitch thrown (in the same at bat obviously):
```Previous pitchRHP to RHHRHP to LHHLHP to RHHLHP to LHHAverage
Fastball-0.36-0.23-1.02-0.59-0.47Changeup0.390.281.792.050.82Curveball0.331.341.090.510.91Slider-0.171.330.700.630.44```
I bet you were expecting the high inside fastball to be most effective when thrown after an off-speed pitch. So was I. It turns out to be quite the opposite. On average, a high inside fastball is always more effective when thrown after another fastball. In fact, a high inside fastball is actually significantly worse than average when thrown after an off-speed pitch.

That actually shouldn't surprise you. A while back, Josh Kalk ran the numbers on how effective each pitch was based on the pitch that preceded it, and found that a fastball was always worse when it followed an off-speed pitch. That, along with what I found today, contradicts conventional wisdom that pitching backwards is an effective strategy.

### Backing them off the plate

Another of the traditional claims of the high inside fastball is that it will improve the following pitches in the at-bat, because the batter is aware of that pitch and will be more timid. Now whether that is actually the case, I don't know; however, we can see how much the run value of each pitch type improves when it's thrown after a high inside fastballs:
`Next pitchRHP to RHHRHP to LHHLHP to RHHLHP to LHHAverageFastball0.380.11-0.170.420.19Changeup0.110.57-0.09-1.880.16Curveball1.360.641.71-0.680.94Slider0.010.50-0.360.230.13`
These results are really surprising. It turns out that all major pitch types are significantly worse than the high inside fastball. This isn't a miscalculation either, at least I don't think. From 2007-2009, when a curveball follows a fastball from a RHP pitcher to a RHH, the run value of that curveball is -.31 runs per 100 pitches. That's consistent with the findings Kalk had in the link I posted above. However, once you add a qualifier for the "first" pitch, plugging in the restraints for the high inside fastball, the rv100 jumps way up to 1.01. It's possible that it's simply a function of sample size (there have been only 956 such pitches); but that's still a huge swing.

So while the high inside fastball may actually back batters off the plate (I assume it does, but we can't be sure), that actually has a negative affect on future pitches in the at-bat. Why that is the case needs to be studied in more detail; however, this article is becoming pretty long, so that will have to wait for another day.

### Conclusion

We've see that regardless of batter or pitcher hand, and, for the most part, independent of pitch speed, the high fastball is an amazingly effective pitch. It also works much better off fastballs then it does off off-speed pitches, and actually makes the following pitches in the at-bat worse than they will normally be. Still, it remains one of the best pitches in baseball simply because of the value it has in itself.

So why don't pitchers throw it all of the time? Well, there are two reasons. The first one has to do with Game Theory. The high inside fastball is so effective in part because it isn't thrown that often. If every pitch were a fastball up and in, the batters would adjust and start to hit it much better.

The second reason is probably the more prominent one. Pitchers don't have perfect control. In fact, a lot of them have pretty bad control. Even Roy Halladay has thrown a ball 96 times in his career with a 3-0 count, and he's one of the good ones. So when a pitcher goes up and in with the fastball, the ball won't always go where it's intended.

And what happens when you try to go up and in and miss? Well, the most likely outcomes are that the ball ends up either high, inside, middle in or center up. As you can imagine, the value of fastballs in those locations is not as good as the ones up and in. The actual effect is best observed like this:

These may be a little hard to digest at first, but I promise you they are information. The first graph shows how good a fastball is in the high zone (as in the zone that I've been calling the high inside fastball zone), based on its horizontal location. It's not labeled, but the y axis is rv100. I've also marked where the high inside fastball is. You can see that for both RHH and LHH, the value peaks inside the high inside zone. The second graph is the same thing, but for fastballs in the inside zone, based on their vertical location. Again, you see the value of a fastball peaks when it is high and inside.

You also should notice how much the value drops once you leave the shaded zones. That raises the concept of pitch leverage: The high inside fastball may be one of the best pitches to throw, but it is also one of the riskiest.

References and Resources
PITCHf/x data from MLBAM and Sportvision, and I am eternally grateful that this stuff is still available to the public. The pitch classifications used were the ones provided by Gameday and unfortunately may not be 100 percent accurate. However, fastballs are pretty easy to classify, so I trust that they are pretty good.

Nick is a Cardinals fan living in LA. He also writes for Viva El Birdos. He welcomes questions and comments via email