Aaron Nola’s Sinker and the Called Strike

I already wrote about Aaron Nola this year. So, too, have Eno Sarris, August Fagerstrom and Jeff Sullivan. He’s been a big deal.

When I wrote about Nola — barely a month ago, at this point — he kind of took the backseat to rotation-mate Vincent Velasquez, who had recently struck out 16 hitters in a dominant complete game. However, since VV’s first two starts, during which he struck out a combined 25 hitters, he hasn’t struck out more than six hitters in a single game and has shown lapses in command.

Meanwhile, Nola has, somewhat quietly, turned in one of the season’s best first six weeks. He ranks third in pitcher WAR (wins above replacement) behind Clayton Kershaw and the underrated Jose Quintana. But WAR is partly a function of playing time, so this might be an unfair comparison for, say, Kyle Hendricks, who has started two fewer games than Nola.

Still, Nola dominates in terms of the defense-independent rate metrics as well, ranking third in xFIP (2.38) and second in FIP (2.14) among all qualified starters. If I showed you Noah Syndergaard’s stats next to Nola’s, and you didn’t already know that Thor wasn’t actually a human being, you might not be able to tell the difference between them:

A Probably Unexpected Comparison
Name IP/GS K/9 BB/9 GB% ERA FIP xFIP WAR/GS
Noah Syndergaard 6.62 10.68 1.75 56.5% 2.53 2.20 2.37 0.229
Aaron Nola 6.63 9.85 1.53 56.0% 2.89 2.14 2.38 0.238

The cells highlighted orange indicate which pitcher trumps the other in a particular category. Yet you can see that the two, from walk rate (BB/9) to ground ball rate (GB%) to the FIPs, are almost identical. More impressively, however, might be that Nola, by mere decimal points, has thrown more innings and generated more WAR per start than Syndergaard.

Now I’m just listing accomplishments, which isn’t really analysis as much as it is making heart-eyes-emojis, but: Nola has thrown 7-plus innings in more than half of his career starts. For comparison, Thor has accomplished such in only about 40 percent of his starts.

But none of this is why I’m here. Nola’s most interesting trait, despite all of this, doesn’t even seem especially interesting. Like, it’s not that sexy, you know? Because I’m not about to say, Nola leads all qualified pitchers in swinging strike rate. No, that’s not it at all. It’s almost the opposite.

Nola currently induces the fewest swings on pitches in the zone (Z-Swing%). It’s fascinating, because it explains why Nola has the third-most backwards K’s in Major League Baseball right now. It’s the kind of skill that has fueled Rich Hill‘s bizarre late-30s success and recently breathed life into Rick Porcello’s mostly pedestrian career.

But this is a great skill for Nola to have because he, behind only Bartolo Colon, leads MLB in zone percentage (Zone%). That’s right: the dude who induces the fewest swings on pitches in the zone peppers the zone more often than almost anyone else. Assuming that pitches in the zone are called strikes — as we know, that’s not always the case, but let’s assume it is for this exercise — we can conclude Nola has stolen far more strikes than anyone else:

Called Strikes (% of Pitches Thrown)
Name Z-Looking% Zone% Looking Strike%
Aaron Nola 46.90% 54.30% 25.5%
Rich Hill 44.00% 51.00% 22.4%
Kyle Hendricks 42.60% 50.80% 21.6%
Doug Fister 44.80% 46.20% 20.7%
Bartolo Colon 36.90% 55.90% 20.6%
As of May 15, 2016
Z-Looking% = 1 — Z-Swing%

I don’t know if this is a healthy way to thrive, let alone a healthy way to live. Hendricks, like Quintana, is a very underrated pitcher. So is the timeless, ageless Colon. As aforementioned, Hill has revitalized his career, and even Fister has experienced occasional success.

But if you expand the list, which includes more than 100 starting pitchers, names such as Jose Fernandez, Clayton Kershaw, Chris Sale and Madison Bumgarner litter the top 20. This isn’t a random group of players, and this kind of skill isn’t reserved to the undeserving. Excellent pitchers succeed at fooling their opponents.

We place a lot of value on swinging strikes. They’re tangible, measurable, discrete events that help quantify pitcher success. But there’s merit to taking advantage of hitters’ passivity. According to Baseball Savant, hitters have swung at only 28 percent of first pitches this season. Nola, perhaps unsurprisingly, ranks 13th in first-pitch strike percentage (F-Strike%), so a lot of those strikes he’s stealing are the product of his intelligence as a pitcher.

But he’s doing other things, too, that fool the snot of hitters and prevent them from lifting their bats from their shoulders. For whatever reason, hitters haven’t wanted any part of Nola’s sinker. It’s not an especially effective pitch in a vacuum; it notches a meager 3.9% swinging strike rate, yet has notched strikeouts roughly 22% of the time. Normally, that would alarm me.

I linked to Sullivan’s post — the one about league-dominating curveball — up top. But Nola’s sinker ranks third in MLB behind Sale and Marcus Stroman, and that’s because it, too, is especially unique. Nola’s pitch has the least vertical movement and, among righties, the most horizontal movement of any sinker in the game:

Sinker/Two-Seam Fastball Movement
Rk (RHP) Name FT-X RK (All) Name FT-Z
1 Aaron Nola -11.3 73 Aaron Nola 2.6
2 Jeff Samardzija -9.9 72 Marcus Stroman 2.6
3 Carlos Martinez -9.8 71 Jeff Samardzija 3.6
4 Jeremy Hellickson -9.8 70 Jon Niese 3.7
5 Yordano Ventura -9.7 69 Jaime Garcia 4.0
Out of 73 qualified starters.

FT-X = horizontal movement, two-seam fastball
FT-Z = vertical movement, two-seam fastball

It’s a unique pitch; Jeff Samardzija’s sinker comes close, but something about it (the velocity, perhaps?) doesn’t leave bats on shoulders the way Nola’s does.

While Nola’s sinker isn’t effective in the traditionally sabermetric sense of the word, it is effective, registering the highest put-away rate in the sport among sinkers, and it’s not even that close. Coupled with a wunderkind curveball, it has catapulted Nola into the (justifiably dormant) National League Cy Young discussion that includes Kershaw, Syndergaard and Jake Arrieta. Philadelphia may have already found the heir to Cliff Lee’s throne.





Two-time FSWA award winner, including 2018 Baseball Writer of the Year, and 8-time award finalist. Featured in Lindy's magazine (2018, 2019), Rotowire magazine (2021), and Baseball Prospectus (2022, 2023). Biased toward a nicely rolled baseball pant.

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TheWrightStache
7 years ago

The Cliff Lee comparison is particularly apt. In Sullivan’s farewell article to Lee, he summarized Lee’s plan of attack “1. Throw strikes 2. All the time 3. And make them good.” Nola’s zone % is a dead ringer for Lee’s, and his arsenal is incredibly similar, if less deep, than Lee’s (Lee worked in a cutter fairly often, and tossed an occasional slider allegedly, while Nola sticks four-seam, two-seam, curve and change). Nola’s pace is damn near identical to Lee’s, too. Heir to the throne indeed.