Will Max Castillo and Carlos Hernandez Make Adjustments to Contribute to the Royals Bullpen in 2023?

Last season, the Royals ranked 27th in bullpen ERA, 28th in H/9 (hits allowed per nine innings), and 30th in WHIP and BB/9 (walks per nine innings). It was a frustrating development to see for Royals fans, especially since the bullpen was so key to Kansas City’s success from 2013 through 2017. (Who could forget HDH (Kelvin Herrera-Wade Davis-Greg Holland), after all?)

Safe to say, based on these metrics (as well as the numbers from the pitching staff overall), it was not a surprise that owner John Sherman and new head of baseball operations JJ Sherman decided to part ways with not just pitching coach Cal Eldred, but manager Mike Matheny as well.

In order to improve a young pitching staff in 2023 and beyond, the Royals have not just hired a new manager (Matt Quatraro) and pitching coach (Brian Sweeney), but they also have changed a lot in the structure of their coaching staff to help address those starting pitching and bullpen issues.

Kansas City has not just added a new assistant pitching coach in Zach Bove, but they have also re-structured the pitching development staff to help transition pitchers from the Minors to the Majors.

Plenty of pitchers in the Royals system will be priorities for the Royals coaching staff and pitching development team this offseason (Jackson Kowar was one I already talked about on the blog). That said, there are two pitchers who particularly stand out, especially since this Spring Training may be a crucial period of time for them from a roster standpoint.

Those pitchers are Max Castillo and Carlos Hernandez, who have pitched in both the rotation and the bullpen for the Royals, but failed to find success in either role last season.

Both pitchers’ futures in Kansas City are hazy for different reasons. And because of that murkiness in regard to their futures, it could put their spots on the active roster in jeopardy on Opening Day in 2023.

Let’s take a look at each pitcher individually, what positive both pitchers could bring to the Royals pitching staff in 2023, and the challenges that they will face as well this Spring when they report to camp in Surprise in February.

Can Castillo Find His Control Again?

It’s not a surprise that Castillo, like many Royals pitchers who were acquired from other organizations, struggled with walks in Kansas City in 2022.

Castillo only saw limited action at the Major League level last season, both with the Blue Jays and the Royals. Before being traded to Kansas City, he only made nine appearances and pitched 20.2 innings for Toronto. With the Royals, he made five appearances and pitched 18.2 innings.

Unfortunately for the Royals, it was almost like Kansas City received a completely different Castillo from Toronto. That can be seen in the data splits below, via Fangraphs:

Castillo did struggle with home runs in Toronto, and that issue carried over with him to Kansas City.

In fact, his HR/FB rate was actually one percent lower with the Royals than with the Blue Jays. While Castillo only had a 3.05 ERA with the Jays, his high HR/FB rates, and abnormally low BABIP (.212) were two key reasons why his FIP was 1.37 points higher than his ERA in Toronto.

So, there was to be some expected regression for Castillo in Kansas City, especially once he garnered more innings at the Major League level.

However, one of the big changes Castillo saw in his transition from Toronto to Kansas City was the increase in walks, and the struggle to throw strikes consistently with the Royals.

Castillo’s K/9 remained around the same as a Royal (only a 0.51 difference), but his BB/9 increased by 2.64 points from Toronto to Kansas City. Not surprisingly, his CSW rate (called strike plus whiff rate) also decreased from 27.5 percent with the Blue Jays to 22.6 percent with the Royals.

When looking at his plate discipline data via Fangraphs from a year ago though, his other metrics in this category painted a more complicated story.

Castillo actually threw the ball in the strike zone 5.2 percent more with the Royals, and actually threw more first-pitch strikes as well (2.5 percent more to be specific). And yet, his called-strike percentage dropped by 4.5 percent, which is a big reason why his CSW rate dropped so heavily after being traded.

What was the reason? Well, hitters adjusted, and simply were more aggressive against Castillo, especially after moving to Kansas City.

Opposing hitters’ swing percentage overall increased by 2.8 percentage points, and they also increased their swings on pitches in the strike zone by five percent as well. Castillo simply became more predictable, and thus, he had to be more creative with where he threw his pitches during his time with the Royals. This often led to him missing the strike zone more frequently with the Royals, and hitters pouncing on his pitches that WERE in the strike zone.

That wasn’t the case in his short tenure in Toronto. Here’s an example of Castillo getting Justin Upton looking on a strike-three changeup back when Castillo was on the Jays.

The command on the pitch isn’t great, as it is right down the middle. However, the pitch selection is solid, as the changeup on a 3-2 count freezes Upton, who’s obviously sitting fastball.

Let’s fast forward to September to one of his final outings of the year with the Royals against the Tigers.

Castillo makes the same mistake in the zone against Harold Castro, but he opts for a four-seamer in a 2-0 count rather than his changeup, which is Castillo’s better pitch. As expected, Castro sits on the four-seamer and blasts it over the right-center wall at Comerica Park.

A big issue that could have contributed to Castillo’s control and walk issues may have just simply been a matter of pitch mix.

Here’s a look at his pitch usage breakdown splits via Fangraphs, and it’s interesting how Castillo utilized his changeup less and slider more in Kansas City.

Castillo’s changeup was worth -1 run on a run value end last season, according to Savant. His slider on the other hand? That was worth +2 runs, his second-worst pitch on a run-value end (his four-seamer was worth +6 runs).

It will be interesting to see if Sweeney and the coaching staff will be able to tap into a more effective pitch mix and better sequencing from Castillo this Offseason and Spring.

Is Hernandez’s Clock Ticking in Kansas City?

Castillo obviously has his issues, but the good thing for the Royals is that they have time to work on his development. The 23-year-old has two Minor League options, and it is likely that the Royals will continue to have Castillo work on his pitch mix and sequencing in Omaha in a more “development-focused” environment.

Hernandez on the other hand is out of Minor League options. That means if Hernandez doesn’t make the active roster out of Spring Training, the Royals will have to designate him for assignment, which could mean him being claimed on waivers.

That’s a primary reason why Roster Resource lists him as a long reliever on their projected Royals Depth Chart for 2023.

Unfortunately, it’s hard to determine what kind of role Hernandez will have in Kansas City in 2023 or beyond, should the Royals decide to hold onto him.

In 2021, Hernandez finished the year strong in the Royals rotation, as he ended up producing a 3.68 ERA and 1.0 fWAR in 24 appearances and 85.1 IP. There was some thought that Hernandez could develop into a dependable starter in the long term for the Royals, especially with a four-seam fastball that could sit in the upper 90s and even 100 MPH range.

Unfortunately, the now 25-year-old pitcher struggled overall last season, as he produced a 7.39 ERA and -0.2 fWAR in 27 appearances (including 7 starts) and 56 innings pitched. By the end of the season, the Royals had pretty much transitioned Hernandez to the bullpen full-time, but the numbers weren’t exactly promising in the move, especially when one looks at his splits via Fangraphs.

Yes, the reliever numbers were better on an ERA, wOBA, and K/BB ratio end (0.80 as a starter; 1.73 as a reliever). That being said, the bar was set so low for Hernandez due to his struggles as a starter. It wasn’t going to be difficult to surpass his starter numbers in the move to relief.

But when Royals fans take away the comparison and just look at the relief numbers on their own, Hernandez still was a mess. It’s going to be hard for him to succeed in any kind of bullpen role long-term if he’s posting a K/BB ratio under two, and an ERA over five.

The big difference for Hernandez from 2021 to 2022 was the decline in the effectiveness of his four-seam fastball.

Here is a look at how Hernandez’s four-seamer has fared on a run-value/ end over the last three seasons, according to Baseball Savant.

In 2020 and 2021, the four-seamer was a positive pitch for Hernandez. While the run value was eight runs better in 2021 in comparison to 2020, they both had the same run value per 100 pitches (RV/100) mark of -1.1. In addition, in both seasons, he also generated strong whiff (22.2 percent) and K rates as well (14.7 in 2020; 18.7 in 2021) with his four-seam fastball.

That all changed in 2022, unfortunately.

His run value mark in 2022 was 20 runs worse than his 2021 total, and his RV/100 was 3.2 runs worse as well. The whiff rate dipped by nearly five points to 17.8, and the K rate dramatically dropped 12.6 percentage points in 2022 from 2021. Lastly, hitters made more productive contact against the four-seamer, as the pitch’s wOBA went from .327 in 2021 to .450 in 2022.

When looking at his approach data via Pitcher List, a big reason for the production decline in Hernandez’s fastball was due to his poor command of the pitch.

That is especially evident in his Hi-Loc (high location) and He-Loc (middle-middle or “heart”) percentage differences from 2021 to 2022, which can be scrolled through below:

Hernandez’s Hi-Loc percentage decreased and his He-Loc percentage increased from 2021 to 2022. One would want to see opposite trends from a pitcher’s four-seamer from year to year.

Hernandez threw his four-seamer in the “heart” of the strike zone 6.8 percent of the time, and that often hurt him in big ways last season.

Below is an example of Hernandez throwing a four-seamer at 97 MPH, but in that middle-middle area to Chicago’s Eloy Jimenez, and he is able to crush it deep center field for a home run.

Now, let’s take a look at Hernandez back in 2021 against Sergio Alcantara of the Chicago Cubs. Hernandez throws his four-seamer at the same velocity (97 MPH), but he locates it in that Hi-Loc area.

The result is much different for Hernandez against Alcantara.

In a bullpen role, Hernandez’s four-seamer will be more important than ever. He obviously has the velocity to succeed with it, as it ranked in the 91st percentile in velocity, according to Savant. But the command on the four-seamer was a major issue for Hernandez in 2022, and that was a big reason why his ERA pretty much doubled from 2021 to 2022.

Sweeney and company will have a lot less time to work with Hernandez this offseason and Spring, especially with him being out of Minor League options.

Which makes this Cactus League campaign a “make or break” one for Hernandez.

If he doesn’t show progress with that four-seam command by the middle of March in Arizona, it is likely that Hernandez will be pitching in a different organization by Opening Day in 2023.

Photo Credit: Tommy Gilligan-USA TODAY Sports


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