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Javy Guerra’s new fastball could help him break out in Brewers bullpen

Guerra’s new four-seamer isn’t just his best pitch, it might be one of the best in baseball

Houston Astros v Tampa Bay Rays Photo by Mike Ehrmann/Getty Images

The Brewers created several openings in their bullpen when they cut ties with Brent Suter, Brad Boxberger, Trevor Gott, Luis Perdomo, and Jandel Gustave earlier this month, but they added to their relief corps by acquiring Javy Guerra in a trade with the Tampa Bay Rays.

Guerra signed with the Boston Red Sox as an international free agent in 2012 and began his career as an infielder. He cracked the big leagues in 2018 as a member of the San Diego Padres.

His bat failed to develop, however. Guerra managed just a .665 OPS in his minor-league career and recorded two hits in a 13-game debut, prompting the Padres to convert him to the mound in 2019.

As such, the 27-year-old is a relatively inexperienced pitcher, but there’s no denying the talent in his arm. Guerra’s sinker routinely sits in the upper 90s and can touch triple digits.

Despite that impressive raw stuff, the results have yet to come together for Guerra. In 44 big-league appearances, he has posted a 6.60 ERA, 5.41 FIP, and 5.18 DRA.

Guerra’s 10.3% walk rate would be high for most pitchers, but it’s rather impressive for someone who recently converted to pitching. The greater issue is that he generates very few swinging strikes with his power stuff. Just 7.1% of his total pitches have gone for swings and misses, producing a 15.3% strikeout rate that isn’t nearly enough to offset the walks.

It was more of the same in 2022, as Guerra finished with a 5.00 ERA and 6.17 FIP in 18 appearances between the Padres and Rays. His strikeout and walk rates both took steps backward, as he issued more free passes (13.4%) than punchouts (12.2%). His swinging strike rate also fell to 5.3%.

Those numbers don’t look impressive, yet General Manager Matt Arnold believes Guerra can become a valuable piece at the back end of the Milwaukee bullpen.

You wouldn’t know it from his surface numbers, but Guerra found something in 2022 that positions him for a step forward next season: a four-seam fastball, and an exceptional one at that.

While Guerra’s arsenal has always been headlined by his blazing sinker, he used a more balanced mix of sinkers (44%) and four-seamers (32.8%) in his first season as a pitcher. However, the movement profile of his four-seamer was too similar to his sinker, and like the sinker, he typically threw it in the bottom third of the zone.

In an admittedly small sample of 11 plate appearances, opponents teed off on this version of Guerra’s fastball. They recorded four hits, including two doubles and a home run. More notably, Guerra’s four-seam fastball induced whiffs on a paltry 14.3% of swings.

In the wake of that poor performance, Guerra scrapped his four-seamer almost completely and leaned heavily on his sinker.

The four-seamer reappeared in 2022, but it is now a noticeably different pitch than the previous iteration.

According to Pitch Info, Guerra chopped over four inches of vertical movement (or sink) off his four-seam fastball. The new shape of his four-seamer is beneficial for a few reasons.

First, it separates his four-seamer and sinker, producing two different fastballs instead of the indistinct mix of a few years ago. Observe how the gap between Guerra’s four-seamer and sinker has increased in the chart below.

Second, Guerra’s four-seamer now has the rising effect that allows many pitchers (think Gerrit Cole or Josh Hader) to excel with their fastballs in the upper third of the zone.

According to Baseball Savant, the “rise” of Guerra’s four-seamer has gone from 0.9 inches below average to an elite 2.9 inches above average.

Third, Guerra’s new four-seamer distinguishes him from other hard-throwing relievers. In addition to eliminating sink, he also changed the horizontal behavior of the pitch.

The horizontal movement of Guerra’s four-seamer has increased from 3.2 inches below average to 1.7 inches above average.

This gives Guerra a four-seamer with both rising and tailing action as it approaches the hitter.

How unique is Guerra’s new four-seamer? Look at his would-be contemporaries atop the vertical movement leaderboard for four-seamers.

Baseball Savant

Most of the best rising fastballs are either straight or have slight cutting action. Guerra’s is one of the only four-seamers in the game with elite rise and solid run, a look that hitters are not used to seeing.

After frequently throwing his old four-seamer below the belt, Guerra honed in on the upper third of the zone with his new and improved one.

Baseball Savant

The results were fantastic. Opponents managed just one hit (a single) against Guerra’s four-seamer in 2022 and whiffed on 30.4% of swings.

The problem is that Guerra largely kept his four-seamer in his back pocket, throwing it just 15.5% of the time. Meanwhile, he continued to turn his sinker at a 55.2% rate.

Guerra’s sinker still deserves attention because it has strong running action of its own (2.4 inches above average). It could prove useful for jamming hitters and generating weak contact. However, its 9.6% whiff rate is the main culprit for Guerra’s poor strikeout rate.

While he can still mix in the sinker, Guerra’s new four-seamer is his best pitch and has the potential to be one of the best in any big-league bullpen. If the plan is to make it his primary pitch moving forward, Arnold’s belief that Guerra can become a high-leverage arm may not be far-fetched.

Statistics courtesy of Baseball Savant, Brooks Baseball, FanGraphs, and Baseball Prospectus.