What Separates Jake Arrieta From Trevor Bauer?

If you attempted to characterize the starters for Game Two of the World Series merely by arsenal alone, you might end up somewhere you didn’t expect: the same place. Cubs right-hander Jake Arrieta throws a four-seam fastball with ride and good velocity; a sinker he’s gone to more often this year; a strong, harder breaking ball; an excellent, bigger breaking ball; and a change he doesn’t use very often. As for Trevor Bauer… Well, huh: he has the same stuff.

Maybe you scoff, because of the differences in the results. Arrieta has produced three consecutive excellent seasons; Bauer has shown promise and improvement, but seemingly not on Arrieta’s level. Regardless, the similarities are present — and remain so, even if you take a more numbers-based approach to the analysis.

Take all the starting pitchers who threw more than 150 innings in 2016. Remove all the pitchers who didn’t throw a changeup at least 3% of the time. (Arrieta doesn’t use his change much, but he has one.) Now remove all the pitchers who don’t use a curve at least 10%. (Both of these guys have good curves, even if Bauer’s might be bigger.) Because it’s hard to even know what their harder breaking balls are, combine cutters and sliders and remove everyone that doesn’t throw one at least 10% of the time. Now remove everyone with average velocity or below.

How many of the original 84 pitchers do you think you have left? I’ll tell you: four. Jon Gray, Justin Verlander, Arrieta and Bauer. Now we can eliminate Verlander and Gray because neither uses a two-seamer or sinker very often.

Tonight’s Game Two starters are very similar in terms of arsenal:

Okay, fine, they throw the same things. That doesn’t mean they look the same, right? Er…

Let’s look at movement and spin for each pitch these guys throw. There are a few more differences, of course. We are all snowflakes.

Given the same velocity — in this case the exact same velocity — more spin on a fastball is a good thing. Jeff Zimmerman showed that the same 94 mph fastball can vary from 5% whiffs to 9% whiffs based on the spin rate. Zimmerman bucketed his findings into increments of 100, but if you round Arrieta up, his expected whiff rate is 7.9%, Bauer’s 7.4%.

That Arrieta gets a few more whiffs than expected and Bauer gets a few less might have something to do with movement — Bauer gets about average horizontal movement on his four-seam and Arrieta gets more — but I wouldn’t put too much stock in that. For one, separating two- and four-seamers in the data is tough, and for two, Bauer gets more rise, which is traditionally good for pop ups and strikeouts. Not surprisingly, when Bauer relied more on the four-seamer before this year, he recorded a better-than-league-average pop-up rate (4.8% to 3.4%) while Arrieta has a below-average pop-up rate for his career (3.1%).

In the end, though, these are very similar pitches, separated only by a little bit of movement and spin.

Arrieta’s spin advantage on the two-seam is less clearly a strength. On the two-seamer, less spin would mean more drop. Then again, both of these two-seamers get less drop than average, and only average horizontal fade. They still do well by whiffs (4.5% is average) because they… go fast.

I thought maybe Bauer’s more over-the-top delivery would account for less drop, but in fact, Arrieta’s release point is two inches higher than his height, while Bauer’s is basically even with his height.

It’s instructive to remember that this is an average, because Bauer is always tinkering with his two-seamer to get more horizontal movement. In his four best games, Bauer had more horizontal movement than Arrieta did in any of his starts this year. At his best, Bauer’s sinker is about as good as Arrieta’s in terms of movement and velocity.

As for the difference in ground-ball rate, that has a little something to do with how the pitchers use their two-seamers. Arrieta throws his lower in the zone and away to lefties, while Bauer throws more front-door sinkers (which he learned from watching Corey Kluber) that run from the lefty’s hip into the zone for a called strike.

Here are the curves. In the case of this pitch, Arrieta and Bauer feature one superior trait each. I found last February that drop and velocity are the qualities that most directly led to whiffs on the curve. Arrieta has the velocity, Bauer the drop. Add in spin rate, and you can see why Arrieta gets more whiffs.

Still, these are both excellent curveballs. Arrieta is 30th and Bauer is 69th in whiff rate among the 199 pitchers that threw 100-plus curveballs this year. Only three pitchers have more drop on their curve than Bauer (only one starter, spin rate king Seth Lugo). Among 80-plus mph curves, only three pitchers have more drop than Jake Arrieta (and only one starter, curve maestro Jameson Taillon).

Here is where we fudge the most, despite the fact that Arrieta has called his pitch a cutter before. His pitch has less spin and much more drop, and looks much more like your typical slider in sum. Bauer’s is pretty much average for a cutter, too.

Again, both have excellent velocity for their pitch types. Given that velocity and drop are the most important aspects for the whiff rate on a slider, and they have great drop relative to their velocities, it’s not surprising that they both have great whiff rates. Arrieta’s slider is the seventh fastest in baseball (bested among starters only by Corey Kluber‘s cutter, and Stephen Strasburg and Noah Syndergaard’s hard sliders). Among sliders that average more than 88 mph, only Chris Archer and Cody Reed appear among the starter who produced more drop than Arrieta. Cutters are harder to study, but only nine pitches have harder cutters than Bauer’s; among 88-plus mph cutters, his drop is about average.

The slider is where Arrieta separated himself the most this year, and it would have been worse had we considered more years. Arrieta’s whiff rate on the slider took a dive down from 17% last year. He’s talked about having lost the pitch, despite the only real difference appearing to be a loss of 1 mph on it — and maybe also the loss of confidence to throw the pitch nearly a third of the time. Regardless, it’s a useful pitch.

So there we have it: similar pitches, thrown similarly. Same pitcher, right? Well, no. There’s certainly something different about them, even if it’s only represented by the results. Bauer was 0-7% better than league average this year, depending on the metric you use. Arrieta, meanwhile, was something more like 15-25% better than league average. One has a Cy Young, the other is more of a young pitcher who hasn’t walked batters at even a league average rate yet.

It’s probably that last dimension that separates them most: command. Every time I talk to Bauer, we talk about command, and this last time he pointed out that he drastically changed his delivery after college and is now just becoming comfortable with those new, less over-the-top mechanics.

Command can lead to better whiff rates across the board through a couple mechanisms. For example: Arrieta was ahead in more counts this season (37% to 34%), which means he had greater opportunities to go for the whiff more often. But command also means that a pitcher can manipulate his pitches and change things pitch to pitch and adjust more readily. Listen to Arrieta on his slider, and you hear how command turns into stuff. “I can manipulate the velocity, I can manipulate the break, depending on the situation, depending on the hitter, depending on the count,” he told me last spring.

You might also want to add deception as a thing that separates the two. Arrieta steps across his body and hides the ball well, and then creates an angle to the plate that is difficult for right-handers. Imagine trying to pick up this changeup:

Bauer’s more traditional approach makes sense given his command problems, as any tweak you give your delivery makes it a bit harder to repeat. So maybe he can show his best command and make his stuff play up closer to Arrieta’s in that dimension, but he won’t be able to improve his deception, especially not between this afternoon and tonight.

These two pitchers have very similar stuff when judged by movement and velocity, and even spin. It’s true that Arrieta’s slider is better, even in a bad year, than Bauer’s cutter, and that’s important because they’re both primary weapons. But even there, they have some similarities, when judged by the things we can measure.

Fortunately for Cubs fans, it’s the two things that we can’t currently measure that favor Arrieta, and favor him heavily.