Elieser Hernandez has reworked his slider

As bad as the Miami Marlins have been this season, it would probably come as a surprise to some that their pitching has been non-horrid. At the All-Star break, their starting staff ranks 21st in the league in fWAR, 13th in ERA, 16th in FIP, and 18th in strikeout-rate. Nothing to brag home to about, but again, not bad for a bad team.

What’s been even better for the Marlins is that their pitching has been on a progressive climb upwards. Since the beginning of May, they rank 19th in fWAR, seventh in ERA, 16th in FIP, and 17th in strikeout-rate among the league. Going back to the start of June, their ranks in those respective categories go as followed: 11th, 6th, 9th, 14th. Looking at the few games they’ve played in July, the pitching staff has put up a 3.24 ERA, topped by only six teams in that constraint.

A lot of this comes in thanks to a trio of sophomore pitchers putting up respectable numbers in Caleb Smith, Pablo Lopez, and Sandy Alcantara. Add in help from Trevor Richards, Nick Anderson, Jose Urena, Elieser Hernandez, and two recent call-ups in Jordan Yamamoto and Zac Gallen and you have yourself a formidable staff.

But what most of the attention going to the recent call-ups and the guys who have been in the league for a few years, there’s someone mentioned above that falls in between that might be going a bit unnoticed. Elieser Hernandez, a 24-year-old former Rule 5 choice of the Marlins back in 2017. Also formerly an Astros prospect, Hernandez got his first taste of big league action last season when he was rushed prematurely to the major league level. Heading into 2018, he hadn’t thrown a pitch above A-ball and while he wasn’t a non-prospect, and he certaintly wasn’t putting up numbers that threw him onto the spotlight.

As to be expected with most Rule 5 draftees, the debut season didn’t go so smoothly for Harnandez. Pitching as both a starter and a reliever, he posted a 5.21 ERA and 5.79 FIP in 65 ²⁄₃ innings, putting up a very pedestrian 6.3 percent K-BB-rate. But with the Marlins officially controlling him after the conclusion of the 2018 season, they sent him down to Triple-A to start the 2019 season, pitching him as a starter full-time. To say his stint down there was a success would be an understatement. Among 112 Pacific Coast League pitchers with at least 40 innings this season Hernandez’s ranks were...

• ERA: 1st
• FIP: 1st
• xFIP: 5th
• K%: 3rd
• K-BB%: 4th

A 1.13 ERA and 2.22 FIP in the Pacific Coast League run environment is no joke.

This dominance earned him a quick return to the major league rotation. In his seven appearances (five starts) at the highest level this season, the surface results look underwhelming. He’s put up a 4.25 ERA and 4.75 FIP in 29 ²⁄₃ innings, with most of his downfall being due to the long ball (1.82 home runs per nine). Look deeper, though, and you’ll find that he’s suffered a bit of bad luck, evidenced by his .320 wOBA verses his .268 xwOBA. In Statcast terms, he’s been dominant at the major league level during his brief time.

Baseball Savant

Out of 180 starting pitchers with at least 100 plate appearances faced, Hernandez ranks eighth in xwOBA, 80th in wOBA, fourth in xBA, and 11th in xSLG. To get a grasp on what Hernandez has done so far, take a look at the company surrounding him on the xwOBA leaderboard.

Looking across the board for Hernandez, what seems to be driving his improvement is his main secondary, his slider. While a serviceable pitch last year (.322 xwOBA), it was held back by its proneness to contact (16.1 strikeout percentage). But it’s been a different story in 2019, as he’s held batters to just a lowly .218 xwOBA, flipping the script on the contact numbers (40.6 strikeout percentage), driving the increase in his strikeouts.

The more interesting thing about Hernandez’s slider this season is how he’s completely revamped it. In 2018, his slider ranked 254th out of 336 pitchers with at least 100 sliders thrown in percentage of drop, standing at negative six percent. In percentage of break, he ranked 206th, at negative 24 percent. This season, out of 349 pitchers with at least 50 sliders thrown, he ranks 349th in percentage of drop at negative 26 percent. In percentage of break, he ranks 168th at zero percent.

Brooks Baseball

Brooks Baseball

A possible signal for the change in movement could be an adjustment of his spin axis. In this scatter chart, it’s visually clear that he’s changed something. The three right-most points on this visual are months in 2019. The rest are from 2018.

Brooks Baseball

It is pretty rare for a Rule 5 selection to turn into anything valuable, let alone work out at all, but Elieser Hernandez could be the rare exception here. His dominance in Triple-A should have put him on watch and now with some adjustments, he’s looked more than impressive at the major league level, giving the Marlins another intriguing pitcher to watch.

Patrick Brennan loves to research pitchers and minor leaguers with data. You can find additional work of his at Royals Review and Royals Farm Report. You can also find him on Twitter @paintingcorner.