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Hayden Wesneski isn’t shy about how confident he is in his slider.

From a stuff perspective, it’s his best pitch. The break on Wesneski’s slider has 18.3 inches of horizontally movement, which (per Statcast) is the fifth-largest break among major league right-handers who’ve thrown at least 50 sliders this season. And setting aside the data, just using the eye-test tells you that it’s nasty.

Hayden Wesneski first MLB strikeout with the slider

18" horizontal movement… only 3 pitchers in MLB average 18" pic.twitter.com/XibLgmNvjN

— Brendan Miller (@brendan_cubs) September 7, 2022

He also doesn’t even have to say out loud that he’s extremely confident in the pitch. For that, we need only look back at the data.

He’s so far been fearless with the slider through two big-league outings, having thrown it more than any other pitch type out of the bullpen with the Cubs (pink bar in the figure below).

Of the 149 pitches he’s thrown at the big league level, Wesneski has attacked hitters with a slider 53 times, 10 times more than his second-most used pitch (sinker) and as many times as his other three pitches (four-seamer, changeup, cutter) combined.

It wasn’t always that way, though. During his first two years of college ball at Sam Houston State, Wesneski said he hardly threw the pitch because he “couldn’t spin it.”

He played around with different arm slots and grips, but it wasn’t until his junior year in 2019 that everything clicked. He found the slot and the grip that’s pretty much the same as it is now. And with that new-found weapon, no wonder he struck out nearly as many batters that year (110) as in his first two seasons combined (114) in 76 2/3 fewer innings.

But when he got to the minors after being drafted by the Yankees in 2019, the supreme confidence in the pitch wasn’t completely there. It was still a very effective pitch, but he wasn’t utilizing it to its full capabilities.

“He had a good slider, but he didn’t know how to use it,” Cubs assistant pitching coach Daniel Moskos, who was Wesneski’s pitching coach during his time in Double-A last year, told CHGO. “He would save it and not use it enough. Like, he’d get to two strikes and wouldn’t throw it. We’d have to twist his arm to get him to throw it.”

Once Wesneski realized how well he could throw the slider, he may have gotten a little too confident in the pitch at the time.

“He started to get overzealous with it and just throw it out of the zone,” Moskos said. “We had to get him back in the zone with it, understand what the strike-to-strike one is, what the strike-to-ball one is.”

“[Moskos] was really helping me through the site of the pitch, throwing it for strikes,” Wesneski told CHGO. “There’s different ways you can do it. There’s the guys that throw it at a spot and let it move, and I’m one of those guys that throws it at the mitt and whatever it does, it does.

“He kind of just gave me the consistency with it, and he told me also to throw it more. I can trust it a little bit, and that’s a big deal with a pitch like that is that it’s so big. Sometimes it’s hard to control, and he gave me the ability to just go, ‘Hey, throw it. It’s gonna play, and if you throw it off, they still have a better chance of swinging.’ You got more room to play with.”

Once the command was there to match his confidence, Wesneski quickly moved up the ranks of the Yankees’ system and debuted in Triple-A at the end of last September. And with the slider helping to lead the way, Wesneski continued to trend up and made his major league debut with the Cubs on Sept. 6 in just his second full season of pro ball.

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Yes, the slider is something he’s got the utmost confidence in, and yes, it can be an elite pitch in the majors.

But Wesneski is smart enough to know that a strong mix of pitches will make him as effective as he can be. The slider is the pitch that can lead him to success, but the fact is he’ll need to be able to mix his pitches well to make that success sustainable.

That idea took shape while Wesneski was working with Moskos in the Yankees’ system. Moskos said Wesneski was mostly relying on his slider and his sinker, but that wasn’t going to be enough. So, during the lost 2020 minor league season and during the summer of 2021, they spent time developing the other three pitches now in his arsenal: four-seam, cutter and changeup.

Success in mixing those five pitches allowed him to rise through the minor league ranks, and he’s now looking to do the same in the big leagues.

The cutter in particular is intriguing. While Statcast was tracking Wesneski’s pitches during his debut, his cutter was being recorded as a slider. But Wesneski clarified that it was in fact a pitch of its own.

“My cutter is like a small slider, so I can throw the gyro if I need to,” Wesneski said.

So far, the pitch has been tracked upwards of 90 mph with similar induced vertical movement to his slider but with about 60-70 percent less sweeping action.

Wesneski describes his cutter as a gyro because it’s thrown at 11:30 (think of this like the time on a clock), but it ends up moving around 10:00. That difference is the third-largest in MLB for cutters, and that’s a reason why his fourth-most-used pitch thus far can have a big impact when he deploys it.

Of all five pitches in his repertoire, he’s thrown changeups the least, making up just 5.4 percent of his offerings.

Even then, the lack of changeups thrown doesn’t mean he lacks confidence in the pitch. He made that much clear when he first met Chicago reporters upon getting called up and was asked what’s working for him when he’s at his best.

“I’d say the changeup’s probably the x-factor pitch if it goes well,” Wesneski said. “I mean, if I have my fastball and my slider, I always have a chance, but if the changeup’s there, then I’ll probably dominate for the most part.”

It’s refreshing in a sense to see that Wesneski understands the need to have more than just his slider working when he’s on the mound. Major league hitters will get more data on him the longer he pitches, and they’ll figure out how he likes to attack them.

But if he can command each of the those pitches whenever he takes the ball, it’ll make it that much tougher for hitters to know what’s coming.

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Another benefit to having a wealth of pitches at this disposal is the idea that he can mix them depending on who’s standing at the plate — and more specifically, on which side of the plate the hitter is standing on.

“We didn’t neglect the fact that he was gonna have to focus on getting lefties out,” Moskos said. “… As a predominantly sinker/slider guy back then [while in the Yankees’ system], you worry about the the left-handed platoon issues.”

That so far hasn’t been an issue in the big leagues, since Wesneski has only faced three lefties thus far, but he and Moskos identified the need to develop pitches to attack left-handed hitters long before either of them arrived in the Cubs organization.

“You see performance numbers dictate a platoon-split disparity,” Moskos said. “The sinker doesn’t play as well to opposite-handed hitters as it does to same-sided. You see different movement profiles play better to opposite-sided hitters versus same-sided hitters, and so you just try and prioritize what your best weapons are to put you in the best position to succeed.”

They believe Wesneski’s slider will play on either side, so there’s no need to mix it up in that sense. But like Moskos said, the sinker hasn’t played as well to lefties as it does to righties for the 12th-ranked prospect (per MLB Pipeline) in the Cubs’ system.

“For the most part, the sinker doesn’t go to lefties, just because they hit it,” Wesneski said. “I’ve gone through it where the sinker has gotten bashed by lefties, and so I don’t throw it unless certain times or certain people.”

So that’s why the duo honed in on developing the four-seamer.

It’s not a pitch Wesneski shies away from throwing to righties, too, but it’s the fastball he goes with when there’s a lefty in the box. Again, he hasn’t had many opportunities to display the platoon mixes because of the lack of lefties he’s gotten to pitch to, but when the time comes that he’s facing hitters on both sides of the plate, expect that to be the way the pitch mix looks — especially while he’s working as a multi-inning reliever like he currently is.

“If you can live off of your top two weapons to each guy, if it’s sinker/slider to righties and four-seam/slider to lefties, so be it,” Moskos said. “Mixing in the occasional cutter or changeup when you need weak contact or a foul ball or something to get to two strikes. But yeah, out of the bullpen, I think you could see a little bit of a more simplified approach.”

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Those are the basics of what Wesneski’s mix will look as he moves forward in his career.

However, opposing lineups can always throw those general mixes out the window. When that happens, both Wesneski and Moskos are confident he’ll be able to attack with what’s needed in any given situation, whether that means pitching backwards (i.e., throwing secondary pitches over fastballs early in the count) or starting hitters off with some velocity.

“I think he’s got enough weapons that he can attack a lineup given what the lineup strengths and weaknesses are,” Moskos said. “He’s still gonna pitch to his strengths the majority of the time, but I just think he’s got enough command and enough weapons to be able to be, like, ‘OK, this is a lineup that handles the four-seam. Maybe I can live off the sinker a little bit more’ or ‘this is the lineup that handles the sinker. I can live off the four-seam’ or ‘this is a lineup that doesn’t chase the slider as much, so I’ll use that early and then try and finish hard.'”

Wesneski also knows there’ll be days ahead when a pitch just isn’t working, and that’ll force him to adjust, too.

“For the most part, I think it’s gonna stay the same, but I say that, and then the next week, I won’t have ‘blank’ pitch,” Wesneski said. “I’ll just go, ‘OK, you know what? I can’t throw it today. I haven’t been throwing it very well today, and so I have to use this pitch instead because it’s been going well.’

“Sometimes throughout an outing, it’s not necessarily, ‘Oh, I’m gonna stick to this usage, and that’s what’s gonna happen.’ It’s one of the things where, ‘Man, I just feel really comfortable with this pitch today. It looks really good. I’m putting in spots,’ and so at that point, it’s kind of one of those things where I’m gonna lean on that.”

Still, when you have a pitch that looks as nasty as Wesneski’s slider often does, that’s what it always comes back to.

Wesneski said neither the Yankees nor the Cubs have tried to mess with his slider, instead focusing on making sure he can properly execute it. He still has to prove he can do that at the big league level over the long haul, and considering he hung two sliders over the heart of the plate that both left the yard during his second outing against the Giants on Sunday, there’s work to be done.

As he moves along in his career, the best version of Wesneski will be the one who can throw any of his pitches whenever he needs to. But when it comes down to it, Wesneski is more than comfortable turning to his slider to get a hitter out.

“[The Cubs] want us to use our best pitches,” Wesneski said. “If you’re gonna get beat, get beat by your No. 1.”