Seung Hwan Oh has faced 25 batters this season, and thus, 25 batters in his major league career. There. You can’t say I didn’t warn you about sample sizes limitations. But sometimes, a number just sticks out at you, and you can’t ignore it. Sometimes, a number is separated so far from the pack that even when you consider the limited sample and factor in the expected regression, it still means something. Sometimes, that number looks like this:

Blink, rub your eyes, do whatever you need to do, and then look at that last column again. More than half of all swings offered against Oh pitches this year have resulted in whiffs. He’s got nearly a 20 percentage point lead over Craig Kimbrel and Ken Giles. Look at that rate of contact inside the zone. Look at it! Oh has gotten whiffs at would-be strikes like Francisco Liriano has gotten whiffs at would-be balls. He’s been completely untouchable. Through 25 batters faced.

The lowest single-season contact rate ever allowed by a qualified reliever was 56% by Aroldis Chapman, in 2014. Both Chapman and Andrew Miller checked in below 60% last year. Oh clearly won’t stay near where he is, and he might not even stay near where Kimbrel is, but his first handful of big league appearances have been about as meaningful as they possibly could be, and I think I’m already comfortable saying that, at the very least, Oh isn’t going to be an easy at-bat for anyone. It seems like the Cardinals have found themselves a real weapon. The question is, just how strong is that weapon?

We already knew some basic information about Oh before he came stateside. We knew that he’s 33 years old, and that he’d pitched professionally in Korea and Japan for more than a decade. We knew that, during that time, he’d earned a reputation as one of the most dominant closers those leagues had ever seen, with more than 350 combined career saves, and we knew that he had two 80-grade nicknames — “Stone Buddha” and “The Final Boss.”

Now, we know more. We know that he’s built like a tank, and likes to wear small shirts that accentuate his physique. We also know plenty more useful information, thanks to PITCHf/x cameras. Like, for example, we know he’s thrown a fastball at 92 around two-thirds of the time, and a slider at 85 the other third, occasionally mixing in a changeup and a curveball. We also know the slider is the driving force behind that ridiculous contact rate. We’re past the basic information, and now we’ve identified the slider. Let’s zoom in.

Oh has a slider, and he’s thrown it 31 times this year. He’s thrown 31 sliders, and it’s been swung at 15 times. Contact has been made just three times. Put another way, for emphasis: 12 of the 15 swings against Oh’s slider have resulted in whiffs this season. Hitters have come up empty 80% of the time.

With both his fastball and slider, Oh has lived on the outside edge of the zone against right-handed batters:

What we see here is a clear plan of attack. What we also appear to see here is impressive command. Oh’s already got a nice little cluster of red. He’s got a spot, and he’s been hitting it. It’s worth remembering that even though Oh is technically a rookie by MLB’s standards, he’s far from one by baseball’s standards. He’s not searching for anything. He’s been crafting and executing this approach for years. He’s just doing it in a different country now.

The slider goes 85, topping out at 87, and maybe it moves a bit more like a cutter. He changes speeds with it based on the situation, sometimes dropping it down to 82. It’s got a particularly low spin rate, which actually correlates strongly with swinging strikes, helping legitimize the notion that this may be a truly elite out pitch in the major leagues. A low spin rate paired with above-average velocity sounds sort of like the Warthen Slider thrown by all those young Mets pitchers. Oh doesn’t quite have their velocity, but there’s still a loose connection to be made there.

I wanted to see who else throws a slider that looks and moves like Oh’s. The easiest way to do this is to steal from my colleague Jeff Sullivan, who’s performed a similar exercise countless times in the past — take velocity, horizontal movement, and vertical movement, and use z-scores to find similarity scores. Except, now, we have useful spin rate information from Statcast at the new BaseballSavant, and so I folded that into the mix, too.

More optimism for Oh, coming right up:

Seung Hwan Oh’s Three Closest Slider Comps Player Velo H. Mov. V. Mov. Spin Seung Hwan Oh 85.6 1.5 3.4 2167 Masahiro Tanaka 83.0 1.3 4.0 2138 Max Scherzer 86.4 1.1 2.7 2302 Johnny Cueto 85.2 0.9 3.1 2345

The three pitchers who throw Oh’s sliders just so happen to be three of the best arms in baseball. As Jeff’s been quick to point out in the past while performing this exercise — this doesn’t take into account command, or the rest of one’s arsenal. Johnny Cueto’s always had elite command. Scherzer’s fastball goes 96. Everyone’s different. But we have some evidence of Oh commanding the slider, and paired with the low spin rate, which should induce whiffs, this table is just a bit more evidence that Oh’s stuff is legit.

Let’s watch an at-bat. It’s against Adonis Garcia, who won’t quickly be mistaken for Giancarlo Stanton, but Garcia’s been an above-average hitter in his major league career, and he’s not prone to strike out. Spoiler alert: Oh made him look silly.

0-0

Fastball. Molina sets up inside, Oh goes too far inside. It’s a first-pitch ball, but at the very least, it sets Oh up to go outside, where he likes to work. Garcia won’t see anything like this pitch for the remainder of the at-bat.

1-0

Slider, low and away, and nasty. The first thing I noticed watching Oh pitch for the first time was how his step toward third base paired with his three-quarters arm slot give him what seem like a particularly challenging angle for right-handed batters, especially for that slider away. No wonder he likes to throw it so much. That he was willing to throw it in an 1-0 count is another indicator of the level of confidence he has in this pitch.

1-1

Oh comes back with that same slider, but yanks it a bit. Garcia doesn’t bite. No worries. It’ll be back.

2-1

See? There it is! Molina sets up a bit higher for this one, and a bit more outside, and Oh hits the spot. Garcia flails. Cardinals manager Mike Matheny had this to say of Oh over the weekend: “…he knows when to expand the zone, throw his slider a little further out or add extra break to it. That comes with time and experience.”

2-2

Garcia had to have known what was coming. Oh missed with the only fastball he threw, and had since thrown three consecutive sliders, two of which made Garcia look bad. He had to have known what was coming, yet he still couldn’t lay off.

This is probably the most dominant at-bat Oh’s had against anyone, but I imagine Garcia isn’t alone in looking this helpless against Oh. The contact rate is unparalleled. The approach is clear and consistent. The slider’s got peripheral numbers that back up its being a legitimate out pitch. It’s 25 batters, yeah. And he’s probably not going to be Craig Kimbrel. But I dare you to find someone who’s looked more unhittable thus far than Seung Hwan Oh.