Why this KC Royals bullpen option is poised for a surprise breakout

Fresh off an exciting 2024 playoff berth, the Kansas City Royals are looking to build on what was arguably a surprising campaign. While their resurgence sparked optimism, a glaring issue stood out — the bullpen lacked stability.

While midseason additions helped solidify the backend of the relief corps — Lucas Erceg emerged as a bright spot amid the inconsistency — the Royals signed established closer Carlos Estévez into the mix this winter, which has helped define roles.

With a strong postseason showing and a clearer sense of direction heading into 2025, expectations for the Royals' relief corps have grown significantly. This spring, several arms have shown they are leaving their 2024 performances behind and attacking the new season with renewed intensity. However, one pitcher, in particular, has stood out among them — left-hander Angel Zerpa, who looks primed for a breakout.

Now entering his fifth major league season, all with Kansas City, Zerpa has steadily progressed from a sporadic call-up to a reliable bullpen piece. In 2024, he took on his most significant workload yet, making a career-high 60 appearances and logging 53.2 innings with a 3.86 ERA. The southpaw also posted 49 strikeouts, saw his K/9 rise from 7.6 to 8.2, and lowered his walk rate.

Despite the improvements, there was still work to be done. Zerpa had the tools, but his effectiveness still needed refinement.

Zerpa is looking strong ahead of KC Royals' 2025 season

Zerpa arrived at spring training determined to take his game to the next level, and the results have caught a lot of eyes. Across eight appearances, he’s thrown eight innings, allowing just two hits while striking out seven and surrendering just one hit-by-pitch. The stats alone are impressive, but the real context lies within the enhancements of his pitch arsenal.

Zerpa has always leaned on his sinker, throwing it 41% of the time and generating a ton of ground balls. But what’s changed is the increased velocity and added break on his secondary pitches.

• Velocity boost: In 2023, Zerpa’s sinker averaged 94.6 mph. By 2024, he boosted it to 96.5 mph. This spring, he’s consistently sitting between 96-97 mph, with multiple outings topping out at 99 mph.
• Sharper slider: His slider now drops at five inches, creating a sharper, more deceptive break.
• Changeup usage: Zerpa has begun utilizing his changeup more frequently, a critical adjustment for keeping hitters off balance.

For Zerpa to enter the conversation as one of the league’s elite relievers, he must refine his ability to neutralize right-handed batters. The best relievers thrive on a strong fastball/changeup combination, typically featuring an 8-12 mph velocity gap. Zerpa’s changeup sits at 88 mph, right on the cusp of perfect alignment with his high-velocity sinker and fastball, making him a nightmare when successfully commanding the strike zone.

His ability to induce uncomfortable swings has been on full display this spring, drawing praise from Royals manager Matt Quatraro, who has indicated Zerpa will be trusted in high-leverage situations this season.

So far, Zerpa is off to a scorching start. While it’s clear he will continue dominating lefty-lefty matchups, his true test will be finding success against right-handers. If he can mix speeds effectively and refine his command, don’t be surprised if he becomes one of the biggest bullpen revelations of the upcoming season.