Elieser Hernandez’s Improved Arsenal Makes Him a Rule 5 Pick to Watch

The Miami Marlins lost 105 games in 2019 under the shadow of their latest rebuild. For this franchise, it seems, hope is eternally just over the horizon. But like many rebuilds, the dispiriting results on the field hid some areas of promise.

In the Marlins’ case, people buzzed about some of their young arms. Sandy Alcantara got everyone the most excited with his 2.3 WAR, followed by guys like Pablo Lopez and Trevor Richards who could be called “serviceable’” which is a compliment for what’s essentially a quad-A team. (Before you boo me, know that I’m an Orioles fan.) Caleb Smith and Jordan Yamamoto also got some interest.

Other teams noticed. The Rays acquired Richards and Nick Anderson in the middle of a playoff run. The Diamondbacks did the same with Marlins hurler Zac Gallen. Down in the minors, hitters like Jazz Chisholm and JJ Bleday get attention alongside pitchers like Sixto Sanchez (what a fantastic name!) and Edward Cabrera.

But not many people got excited about Elieser Hernandez. I can understand why they didn’t: he’s not a household name. The Astros signed Hernandez in 2012 just after their much-heralded change in regimes and leagues. He bounced around their minors for awhile before the Marlins snagged him in the 2017 Rule 5 draft. Unless your name is Johan Santana (or maybe Dan Uggla), no one’s going to get excited if you’re picked in the Rule 5 draft. Heading into 2018, John Sickels gave Hernandez a C+ grade and ranked him 22nd among the team’s prospects.

After joining the Marlins, Hernandez was unspectacular in the minor leagues, posting a 21% strikeout rate and 10% walk rate across three levels. He fared much worse on a major league mound, with a 15.9% strikeout rate and 9.5% walk rate alongside a .337 xWOBA in more than 65 innings. Those disappointing stats contributed to a similarly disappointing -0.5 WAR.

Then things got interesting. In 2019, Hernandez’s minor league strikeout rate jumped to 34.3% while his walk rate fell to 6.9%. After a callup in June, he showed similar improvements, boosting his MLB strikeout rate to 24.1% and enjoying a walk rate of 7.4%. These improved rates helped yield a more palatable xWOBA of .290. He finished the year with 0.1 WAR in more than 82 major league innings, a noticeable improvement from the prior year.

What changed? The following graph shows the pitches we should be focusing on:

As others have noted, Hernandez’s slider stands out as his most improved pitch. The higher whiff rate and lower xWOBA indicate it’s fooling hitters more often.

The following graph shows how Hernandez’s pitch arsenal moves differently, comparing each year to average pitches thrown at similar velocities:

The good news is that Hernandez added horizontal movement to his slider. In 2018, it broke 25% less than sliders thrown at the same velocities; in 2019 it broke just 4% less than average. While still not a league-average sweep, it seems to be good enough to fool hitters often.

An area for improvement may be the pitch’s vertical drop (or lack of it). In 2018, Hernandez’s slider dropped 6% less than the average slider thrown at similar velocity. In 2019 it dropped a whopping 26% less. He reduced the pitch’s vertical drop so much that his slider now has the most “rise” in baseball, meaning it counteracts gravity more than any other:

Sometimes being unique is a good thing, but in this case maybe not. Rise can be good for high-speed, high-spin fastballs, but according to Michael Augustine, sliders with rise but little sweep can hang and get crushed. Hernandez’s slider definitely has rise, and although it has more break than it used to, that break is still below-average.

Diving deeper, the following graph shows how Hernandez has changed each pitch’s spin rate, velocity, and spin direction:

In 2019, Hernandez’s slider spun about 200 rpm faster and along a different axis while traveling about 1.5 mph slower. That’s nice, but what may matter more is how these characteristics help the pitch play off his fastball. Research by Eno Sarris shows that when it comes to sliders, “you want to [make a choice] between mirroring spin (curveballs) or getting spin direction (and velo and drop) closer to your fastball (sliders).”

Hernandez, or whoever’s coaching him, seems to have chosen the latter:

While he’s increased the velocity differential between the two pitches, the spin axis and vertical drop are closer together. Perhaps the large amount of rise in the slider isn’t such a bad thing after all.

Speaking of Hernandez’s fastball, it’s his second-most improved pitch. While its .341 xWOBA against was middle-of-the-pack, it’s better than it was. He’s definitely attacking hitters with it more often:

The low fastball is practically gone, as is some of the east-west spread. Although its spin rate isn’t high, Hernandez’s fastball does have 11% more rise than the average fastball thrown at a similar velocity. This characteristic, along with the different profile of his slider, could explain why he’s comfortable throwing it higher in the zone.

Despite re-shaping his slider and commanding his fastball better, Hernandez’s mechanics appear to be intact. The following graph shows his release points each year:

These are from the catcher’s perspective, and I made the points semi-transparent so you can see clusters and outliers a bit better. In 2019 I see a bit of a shift towards a more over-the-top release. But what stands out to me is that his release points got even more consistent from pitch to pitch:

This ability to hide his release point only adds to the effectiveness of his arsenal.

Elieser Hernandez still has room to improve. He needs to get his home run rate under control, he needs to regain a serviceable changeup, and he needs to figure out his fastball. And just because he’s adjusted to major league hitters doesn’t mean those adjustments will stick. He’ll have to show he can keep up his performance in the face of batters doing their own counter-adjustments.

However, he’s shown the ability to get better at the major league level at a young age. He added movement to his slider and fastball while increasing the spin rate on the former and honing his release. These changes tell me he has a chance to overcome the stigma of his Rule 5 draft status and get out from under the shadow of his fellow prospects.

We hoped you liked reading Elieser Hernandez’s Improved Arsenal Makes Him a Rule 5 Pick to Watch by Ryan Pollack!

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Ryan enjoys characterizing that elusive line between luck and skill in baseball. For more, subscribe to his articles and follow him on Twitter.

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Neat article, I remember when I was surprised to see Hector Noesi getting so many strikeouts too in AAA last year. I remember that since I was more skeptical of Hernandez as he was averaging barely 5 IP per start in AAA.