Should the Royals Transition Carlos Hernández Permanently to the Bullpen?

The Royals lost another tough one today to the Tampa Bay Rays, as they only recorded four hits in a 5-2 loss on Saturday afternoon.

Kris Bubic struggled on the mound against the Rays, as he only went 3.2 IP and allowed four runs on eight hits and two walks. To make matters worse, Bubic didn’t record a single strikeout, and he finished the game with a paltry 13 percent CSW (called strike plus whiff) rate to boot.

However, this isn’t a piece on Bubic, who is starting to cool off in August (4.71 ERA) after posting a 3.28 ERA in six starts and 35.2 IP in July.

Rather, this is a look at Carlos Hernández, who pitched two innings today and allowed one run on two hits. He was recently called up to boost the Royals bullpen after posting a 3.78 ERA in 12 appearances (11 starts) and 50 IP with the Omaha Storm Chasers this season.

Hernández remains a bit of an enigma to the Royals and Royals fans alike.

He possesses some of the most electric stuff in the Royals organization, as his four-seamer can touch 100 MPH with regularity. In fact, against the Rays today, Hernández posted the five fastest pitches of any pitcher today, Tampa Bay included.

All five of those pitches clocked in at over 100 MPH.

And yet, despite the triple-digit four-seamer, the results have been mixed for Hernandez this season.

Currently, he is posting an 8.84 ERA in 10 appearances and 38.2 IP at the Major League level this season. A big reason for his lackluster ERA with the Royals this season has been primarily due to his lack of command, as he has walked 22 batters while only striking out 23. Add that with 57 hits allowed, and a 2.04 WHIP, and it makes sense why Hernández has bounced around between Kansas City and Triple-A Omaha in 2022.

After his starting on May 19th, Hernández has primarily worked out of the bullpen since. Now, it’s difficult to tell if the Royals are planning to develop Hernández as a reliever going forward, or if this is just a temporary solution to help him regain his confidence and command at the Major League level. While the Royals certainly need the help in the bullpen, they also have failed to find a reliable option in the fifth spot of the pitching rotation this year as well.

Let’s take a look at Hernández’s profile, and whether or not a permanent move to the bullpen makes sense for him not just for the remainder of 2022, but 2023 and beyond.


How Has Hernández Fared as a Starter and Reliever This Year?

Hernández has made seven starts and pitched 29.2 innings as a starter this year, and honestly, the results have been abysmal.

As a starter, not only has he produced an ERA of 9.10, but his command has been pretty poor, to put it bluntly. If Royals fans take a look at his starter/reliever splits data, via Fangraphs, it is easy to notice his low strikeout rate and high walk rate. Unfortunately, both subpar rates affect the rest of his other metrics as a pitcher, which can be seen in the table below.

A 6.07 BB/9 is certainly not a great mark in general. But, a K/9 of 4.85 and 0.80 K/BB ratio only amplifies Hernández’s struggles as a starter at the Major League level this season. It’s impossible for any starting pitcher to have any kind of success in the big leagues if they are walking more batters than they are striking out on a regular basis, plain and simple.

In addition, the high number of walks also contributed to a lack of innings as a starter for Hernández this season, especially in April and May. Based on his game logs as a starter this season, via Savant, Hernández only got past the fourth inning once in his seven starts this season (a 5.1 inning performance against the Seattle Mariners on April 24th).

Interestingly enough, Hernández’s pitch mix probably had a lot to do with his struggles as a starter at the beginning of the season.

In his first seven outings, his pitch mix percentage heavily fluctuated from game to game. While his four-seamer still proved to be his primary pitch (he has thrown it 46.2 percent of the time this season), he also utilized his curveball frequently as well at the start of the season.

However, if one checks out his pitch percentage chart by game, via Savant, one can see that he has pretty much phased out the usage of his curveball as a reliever.

As a starter, Hernández’s primary pitch usage was four-seamer, curve, and either splitter or slider, depending on the game. Since moving to the bullpen though, that pitch mix has been pretty much four-seamer, slider, and splitter, with the curve not being used at all in his most recent outing.

Today, he brought it back, but he only threw it six times, good for a percentage of 18 percent.

His switch to the slider as a primary breaking pitch as a reliever has been a wise move. Not only did he produce a 38 percent CSW rate with the pitch today (against a good Rays lineup), but his slider is also generating a 20.5 percent K rate overall this year, which is the best K rate of any of his pitches this year, according to Savant.

A big issue with his knuckle curve is that he often hangs it up in the zone far too often, which was especially true when he was a starter. Just take a look at the pitch heatmap of his knuckle curve this season so far.

That dark red circle in the middle of the strike zone is not ideal, especially when its spin rate ranks in the 21st percentile, according to Savant.

In fact, here’s an example of Hernández hanging it in the zone to Seattle’s JP Crawford in his April 24th start against the Mariners, and he is able to line it easily to the opposite field for an RBI double.

Now, on one hand, the metrics seem to favor the curve over the slider.

Hitters are only generating a .292 wOBA against the curve this year, which is much better than the .392 mark against the slider. Furthermore, opposing hitters’ hard-hit rate against the slider is 15 percent higher than the curve, which is not a good sign either.

However, let’s take a look at Hernández’s slider heatmap.

It still catches too much of the plate, but for the most part, Hernández is able to command the slider a lot more effectively than the curve. This is particularly true in his swinging-strike heatmap of the slider, as a majority of whiffs against the breaking pitch have come in that lower glove-side part of the strike zone.

Here’s an example of Hernández utilizing that slider effectively against Teoscar Hernandez in a July outing against the Toronto Blue Jays.

It’s interesting to note though that Hernández has been much better with his slider as a reliever than as a starter. Here’s a look at his slider metrics back in April and May, when he primarily pitched as a starter for the Royals.

And now, let’s take a look at those slider numbers as a reliever in July and August.

The home run rate is a little higher and the K rate is slightly higher as well. Furthermore, there is an inverse difference in batting average and expected batting average between the two stints (BA against the slider is higher than xBA in April and May; xBA is higher in July and August). This shows that he has gotten a little luckier with the pitch as a reliever.

On the other hand, he is allowing fewer barrels with the slider as a reliever, and the hard-hit rate against the pitch is down as well, which are both promising signs.

Therefore, it is possible that the slider could be a key pitch for him out of the bullpen, especially down the stretch in 2022.


Does the Bullpen Make Sense for Hernández At this Point?

One of the biggest differences that can be seen from Hernández as a reliever is the increased velocity in his four-seamer.

During the beginning of the year, his four-seamer sat in the 93-95 MPH range. Since a move to the bullpen, that average four-seamer velocity has skyrocketed, which can be seen in the game-by-game average velocity chart from Savant below.

Additionally, with the increase in four-seam velocity, Hernández has seen a dip in xwOBA on the pitch, though there was a slight spike in his August 13th outing against the Dodgers (which isn’t too bad considering they absolutely mashed Royals pitching that night).

Here’s a look at that xwOBA chart via Savant:

When Hernández locates the four-seamer well, it can be an impressive swing-and-miss pitch.

Below is an example of Hernández locating it up in the strike zone at 100 MPH against the Dodgers’ Joey Gallo. As expected with a pitch with those characteristics, there is nothing that Gallo, a hitter who is prone to strikeouts, can really do with the pitch.

That pitch above looks a lot more lively than his four-seamer back in April and May, when it was only averaging 95 MPH, according to Savant. Hernández struggled to get that four-seamer by hitters at that velocity, as evidenced by this home run by Cleveland’s Oscar Mercado against the Venezuelan’s four-seamer back on April 11th at the K.

At the beginning of the season, it made sense why the Royals started out Hernández in the rotation.

After all, he posted a 3.68 ERA in 85.2 IP last year, and he had many outings where he held his own against formidable lineups (I remember watching him thrive in person against a tough Yankees lineup on a hot humid night at Kauffman last season).

But even then, so much of his success was BABIP-fueled as a starter, which can be seen in the starter-reliever splits from Fangraphs a season ago.

Hernández benefited heavily as a starter from that .250 BABIP last season. That is evidenced not just by his FIP (4.47 as a starter compared to 3.24 as a reliever) but his xFIP (5.42 as a starter to 4.10 as a reliever) and K/BB ratio (1.46 as a starter to 2.40 as a reliever).

Most of Hernández’s value last year came from his work as a reliever. Unfortunately, because he finished the year as a starter, most Royals fans associated his success in 2021 solely with his work as a starting pitcher. The metrics prove that he is better off pitching out of the bullpen for the Royals both in the short and long term.

And thus, the Royals should probably make that switch permanently with Hernández.

His stuff (especially the four-seam fastball) plays up much better out of the bullpen. Furthermore, he could potentially thrive in late-innings, though for this year, he should just focus on getting work in low-leverage situations for now, just to build his confidence in general as a pitcher at the Major League level.

The Hernández experiment in the rotation was a good and sound idea by the Royals in theory, especially with where he was at in terms of his development as a pitcher in the Royals system (which was thrown off due to the canceled Minor League season in 2020).

But the Royals have options at the end of the rotation, both on the current 40-man roster (Jon Heasley and Jackson Kowar) and in Triple-A Omaha (Austin Cox and Drew Parrish). Rather, they need bullpen help right now and in the future after 2022…

And Hernández can help solve that problem.

Photo Credit: Ron Chenoy-USA TODAY Sports

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