Should this struggling KC Royals reliever be on the chopping block?

Major league bullpens are the quirkiest part about America’s pastime; they’re filled with men whose job is to throw a ball as hard as they can about twenty times in a night, and whether they get paid millions of dollars or get fired the next day depends on the smallest of sample sizes. If the reliever gives up one run, they’ve failed and may have ruined a win. If they succeed, they just did their job, there’s little pomp and circumstance unless it’s for the closer with his flashing lights and fancy music. Imagine if you were either promoted or fired based on your boss’s evaluation of just one hour of your work day? Relief pitching is one of the toughest gigs in the sports world.

Yet, baseball organizations still have to evaluate and manage bullpens despite these small sample sizes and place them in roles that suit them best. Some managers opt for their best arms to pitch in high-leverage situations while others opt for a more traditional setup man and closer dynamic regardless of leverage. And of course, there’s always the left-handed specialists, the middle innings guys, mop-up duty, and the long man.

KC Royals lefty-handed specialist Angel Zerpa is starting to feel the occupational pressure of being a big league reliever and has struggled to really fit into this rather thriving Royals bullpen in 2025.

Does Angel Zerpa fit into this KC Royals bullpen or should he be on the chopping block?

Where does Zerpa fit in?

Zerpa has struggled so far this season to the tune of a 7.20 ERA and a 2.00 WHIP. These are the sorts of numbers that will get you fired. However, Zerpa perhaps is a reliever the Royals should keep in the big leagues despite these ugly outcomes. It can be argued that, if used in a more specialized role, that of the lefty specialist, Zerpa can improve his numbers and be a useful member of the bullpen.

For all intents and purposes, Zerpa throws a sinker, slider, and four-seam fastball. Recent findings have discovered that sinkers are best used against same-handed batters. This has, so far, been true for Zerpa as his sinker has an xwOBA against (a metric used to estimate production on batted balls) of .312 against lefties, 30 points lower than the league average of .342. So far, Zerpa’s sinker has been a solid pitch.

Why has Zerpa struggled?

However, that’s where things fall apart. His slider, the pitch he uses the second most, has fallen off a cliff in terms of production. After a great showing last year (xwOBA against of .272 vs lefties) it has climbed to a below-league average rate of .386. Essentially, his slider has gone from a solid out-pitch to a hittable meatball. It’s even worse against right-handed hitters (.463).

Zerpa also has a third pitch in his four-seam fastball that he’ll use more so against right-handed hitters. It’s never been great, but this year it’s getting tattooed, holding a .548 xwOBA against. Left-handed hitters haven’t hit the four-seamer, but they’ve only faced seven of them. Against right-handers, Zerpa throws four-seamers and sliders, and they’re both getting crushed.

Is there hope for Zerpa?

Despite these ugly findings, there’s still hope for Zerpa. There’s been a noticeable change in the way he’s throwing his slider this year. He’s throwing the slider 3 MPH slower and getting more depth with an additional five inches of drop this season. By the numbers, he’s improved the movement profile of the slider.

However, it has performed much worse this season. Why, exactly? Perhaps it’s due to the fact that the difference in speed between the sinker and the slider diminishes the tunneling effect the slider used to possess; the two pitches no longer look as similar to the hitter as they once did. Getting Zerpa to go back to more of a hard slider should help improve his splits against left-handed hitters.

What other changes can he make?

Now, about that pesky four-seamer. Zerpa currently doesn’t have any plus pitch against right-handed hitters, and really never has in his career. His skillset at the moment is best suited for facing left-handed hitters. However, due to the three-batter rule, he’s going to have to face right-handed hitters. So, what’s the solution? The cutter.

Adding a cutter may be Zerpa’s answer to his issues against right-handed pitching; cutters have been found to be platoon neutralizers because they look like four-seamers until the very last second. Zerpa’s four-seamer is clearly poor, so substituting the cutter for the four-seamer could be his first step to improving against them.

Also, Zerpa’s slider was only slightly below-league average xwOBA against righties last year (.359), so getting back to his harder slider may be the key to improvements against the righties he does face. However, Zerpa should probably be used against right-handed hitters as little as possible.

Should the Royals keep Zerpa?

Zerpa’s numbers are ugly, and Royals fans assuredly must groan when he enters the ballgame. However, Zerpa is an arm worth keeping around due to the Royals limited number of lefty arms. Some minor tweaks to his repertoire can help him get back to being a league-average arm. If the Royals are looking for someone to put on the chopping block when reliever Hunter Harvey comes back, they should look elsewhere.