Since the dawn of time, there’s always been at least one elite major league closer who’s thrown the cutter almost exclusively. By “dawn of time” I mean the mid-1990s, of course, but I think we can all agree that civilization only truly began when humankind discovered frosted tips and cargo shorts. First there was Mariano Rivera, then Kenley Jansen, and now that everything from the ’90s is back in style, there’s Emmanuel Clase.

Clase has been a crucial part of Cleveland’s surprising run to first place in the AL Central; he’s recorded the win or the save in 18 of the Guardians’ 33 victories, and he’s fifth among relievers in WPA. Cleveland’s record in one-run games is 8-6, which isn’t particularly freakish, but the Guardians are 8-2 in one-run games when Clase pitches, and 0-4 when he doesn’t.

Here’s another fun one: Clase is on pace for the first 50-save season in MLB since Edwin Díaz in 2018, and 3.4 WAR, which would be the most by a Guardians reliever since 1988. WAR wasn’t even a stat back then!

Ordinarily I don’t like to mention the Ford Mustang while working for GM, but Baseball Reference’s evaluation of Clase is too fun to ignore. Clase’s ERA+ is 1089; whatever you think about ERA+, I think we can all agree that a four-digit ERA+ is quite remarkable. B-Ref also has Clase at 1.6 WAR, which would put him on pace for the first 5 WAR reliever season since Jonathan Papelbon in 2006, and the highest WAR total by a reliever since Dan Quisenberry in 1983. Not only is 1983, as I established earlier, before the dawn of time, but Quisenberry had to throw 139 innings to accumulate that many WAR.

B-Ref, of course, uses a runs allowed-based WAR; in 26 appearances this season, Clase’s allowed just four runs, only one of them earned. That’s an ERA of 0.36. Zero. Point. Three. Six.

Clase has been one of the best closers in baseball for a while now; he’s led the majors in saves two years running, and has posted an ERA under 1.50 in two of his three full seasons. And contrary to the elite closer stereotype, Clase hasn’t run up gaudy strikeout numbers. His career high in strikeout rate — which, I hasten to add, came in 2022, not this year — is just 28.4%. When Díaz was at his peak, he was striking out 45-50% of opponents.

So what explains Clase’s uncommon success?

Let’s start with the cutter. It’s one of the two hardest cutters in the league. Clase and Camilo Doval both average about 99 mph; nobody else is over 96 mph and only two other pitchers are over 93.5. More than that, there isn’t really a pitch like Clase’s cutter in anyone else’s repertoire.

What separates a cutter from other fastballs is glove-side movement; sinkers and four-seamers tend to ride to the pitcher’s arm side. They also come in a little faster. The fact that Clase can get elite fastball velocity on a pitch that breaks away from same-handed batters is pretty remarkable. The practical impact is that Clase can — and does — run the pitch away from righties basically wherever he wants, while jamming it in on the hands of left-handed batters.

Clase’s cutter averages 98.9 mph with 4.8 inches of glove-side break. The next-fastest pitch with two or more inches of glove-side break, on average, is Corbin Burnes’ cutter — a pretty good pitch by all accounts. Burnes’ cutter averages 95.0 mph with 4.0 inches of glove-side movement, and it’s the only pitch (minimum 100 pitches thrown) with that kind of glove-side break that’s within 6 mph of Clase’s cutter. The hardest pitch that has more glove-side break than Clase’s cutter is Jansen’s cutter, which averages 91.9 mph.

When combining velocity and movement on that scale, a pitcher can usually get whiffs, or at least weak contact, without leaving the strike zone. Indeed, Clase’s opponents are hitting .178 on cutters in the zone, which is 21st out of 258 pitchers who have thrown at least 100 fastballs (all types) in the zone this season. On contact, that number only goes up to .216. But Clase is getting whiffs on only 19.2% of swings on in-zone fastballs; Mason Miller’s whiff rate on those pitches is 42.0%.

So yeah, it’s profitable for Clase to throw cutters in the zone, but not 0.36 ERA and 50 saves profitable. So he’s doing it less. Last year, Clase threw 57.9% of his cutters in the zone; this year that rate is down to 51.4%. (MLB average zone rate on all fastballs is 55.5%; on cutters, it’s 51.5%.)

That’s because throwing pitches in the zone is good, but getting batters to swing at pitches outside the zone is even better. Clase’s chase rate on fastballs outside the zone is 35%, which is the fourth-best mark in the league (minimum 100 fastballs outside the zone; 193 pitchers total). And you’d better believe that if Clase’s last name rhymed with “chase” I would’ve turned in an appropriate pun for the headline of this piece.

The other thing about Clase’s cutter is that it’s really hard to do anything with it even if you do make contact. Clase has allowed only four extra-base hits this year, all doubles. His opponent ISO is .047. Clase is usually among the league leaders in groundball rate; this season is no exception, as his GB/FB ratio is 2.77. But there are grounders and there are grounders. This year, 42.9% of the cutters that have been put in play off Clase have had a launch angle of zero or less. That’s the third-highest rate out of more than 1,200 individual pitches that have generated at least 50 balls in play this year.

I ran that search twice because I didn’t believe that number the first time; only 14 individual pitches have a zero-or-less launch angle rate of 30% or more. Of those, Clase’s cutter is the only one that isn’t a sinker.

So he’s throwing it more — 81.6%, up from his previous full-season career high of 69.2%. Wouldn’t you, if you could get the same results?

The lion’s share of Clase’s remaining pitches are his slider, which has lost a little over a mile an hour in average velocity from 2023, and two miles an hour from 2022, without gaining any more vertical movement.

But he is throwing it lower. Last year, Clase dropped his slider into the lower part of the strike zone, throwing it in the zone 50.3%. That was in the top 20% of pitchers who threw at least 300 sliders. This year, he’s throwing it in the zone just 36.1% of the time, which is 224th out of the 251 pitchers who have thrown at least 50 sliders in 2024.

Here, have a couple heat maps. Clase’s slider location in 2023…

… and in 2024. You can see that red splotch moving down to the southern border of the strike zone. Just as with the cutter, throwing it out of the zone might lead to a few more balls, but it ought to generate more whiffs and weaker contact, too.

Clase’s having a bit of a weird experience in that respect; the swing rate on his slider has actually gone up, from 53.6% to 60.7%. His slider chase rate is up by half, to 48.7%.

At the risk of oversimplifying things, I see no compelling reason for Clase to throw strikes if his opponents have made it clear that they’ll swing at his pitches whether in the zone or not. That’s why Clase, despite throwing the ball in the zone less than in any previous season, also has the lowest walk rate of his career: 2.2%, or two walks on 90 batters faced.

So how does Clase have an 0.36 ERA despite an unremarkable strikeout rate for a closer? When he throws outside the strike zone, hitters swing anyway. When they make contact, they can’t do anything with the ball. He doesn’t walk anyone. He doesn’t allow extra-base hits. Critics of the walks-and-power offensive approach call it excessively boom-or-bust, but Clase is example no. 1 of how hard it is to score by stringing singles together.

He forces opposing offenses to operate in a state of insurmountable primitivity — like something from before the dawn of time.

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