As the regular season quickly approaches the finish line, now is a good time to reflect on the outstanding rookie performances that have taken place across Major League Baseball this season. Paul Skenes, Colton Cowser, and Jackson Merrill have each built an impressive case to take home Rookie of the Year honors in their respective leagues, while players such as Tyler Fitzgerald, Shota Imanaga, and Wilyer Abreu have impressed in their first taste of major league action. Another notable rookie who has put together an impressive debut campaign is Jackson Chourio of the Milwaukee Brewers. As a plus defender with a tantalizing 30-30 offensive upside, Chourio projects to be a fixture in the heart of the Brewers for the foreseeable future.
In May, I wrote an article “Checking In on Wyatt Langford and Jackson Chourio”, where I discussed some struggles that Chourio experienced at the start of the 2024 season. At the time of publication, Chourio had been producing offensively at a level well below league average (69 wRC+), raising questions about how to project his offensive ceiling as a major league player. This article will take a look at the changes Chourio has made to his offensive approach since the beginning of the season, which has allowed him to reclaim his potential as a franchise cornerstone for the Milwaukee Brewers.
Overview
When my initial analysis was published on May 9th, Jackson Chourio was in the middle of a slow start to his major league career. Chourio was striking out at a much higher rate than he possessed during his 2023 minor league season, and he was hitting for less in-game power. Chourio’s batted ball metrics were rather pedestrian, with a 36.3% hard-hit rate and a 6.3% barrel rate. Since publication, Chourio has significantly raised his level of offensive production, producing a wRC+ of 126, tapping into more in-game power while drastically lowering his strikeout rate. Chourio has also been making better quality of contact, producing a 47.9% hard hit rate since May 9th.
The primary concern that I had with Chourio early in the season was his struggles to make contact on four-seam fastballs in the strike zone. With such a glaring weakness that pitchers could easily exploit, I feared that Chourio would not be able to make enough contact to keep pitchers honest within the strike zone, resulting in not only more strikeouts but also seeing fewer good pitches to drive for power since pitchers could repeatedly target this “cold zone”.
As shown by the heat maps above, Chourio possessed a major weakness against outside four-seam fastballs early in the season, resulting in lots of swing-and-miss in this area of the strike zone. This caused Chourio to have an extraordinarily high whiff rate against four-seam fastballs early in the season (35.6% whiff rate) and was likely a major contributor to his high early-season strikeout rate.
Comparing Chourio’s four-seam fastball heat maps from before and after May 9th, it appears that Chourio has closed the hole that he used to have on the outer third of the plate. While he still displays a propensity to chase four-seamers located above the zone, closing the hole on the outer third of the plate has allowed him to make more contact against four-seam fastballs, which not only helped lower his strikeout rate but has also kept pitchers honest and forced them to utilize multiple offerings to Chourio as opposed to relying on the four-seamer.
I also mentioned back in May that Chourio had a swing-and-miss issue with sliders, and hypothesized that “perhaps improving his contact ability against the four-seamer will result in him seeing pitches better which will in turn positively impact his bat-to-ball ability against sliders.” As shown by the table above, the improvements that Chourio has made regarding making contact against outside fastballs have had a positive effect on his bat-to-ball ability against sliders, as he has since lowered his whiff rate (33.3% to 31.3%) and increased his wOBA (.248 to .348) against these pitches since May 9th. These adjustments that Chourio has made to make more contact against four-seam fastballs and sliders have been impressive, and have alleviated any concerns about his bat-to-ball ability that may have been present during the first month of his major league career.
Bat Tracking
Another change that I have noticed in Chourio’s offensive profile is that he has been hitting the ball harder since May 9th. While his barrel rate has remained relatively constant, Chourio has produced a 47.9% hard hit rate since May 9th, compared to a 36.3% hard hit rate over the first month of the season. Since my initial evaluation of Chourio, Statcast has publically released its bat tracking metrics, allowing us to look at Chourio’s bat tracking metrics to find an explanation for his improved contact quality.
As shown by the table above, Chourio’s average bat speed has remained the same, but his squared-up rate and blast rate has increased dramatically since May 9th. As defined by Statcast, “squared up” is a batted ball that achieves at least 80% of its maximum possible exit velocity (as determined by swing and pitch speed), which is only possible if the ball hits the sweet spot of the bat. A “blast” is a batted ball that is “squared up” with a minimal bat speed requirement, serving as a measure of contact efficiency. In addition to the improvements he has made in bat-to-ball ability throughout the season, these metrics indicate that Chourio is also making more efficient contact by displaying an improved ability to make contact with pitches on the sweet spot of the bat.
Grouping his bat tracking data by pitch type can provide a clearer explanation for how Chourio has made adjustments against four-seamers and sliders this season. Chourio has swung at four-seam fastballs with a 1.1 mph faster average bat speed since May 9th and has increased his squared-up and blast rates which has resulted in him producing a higher quality of contact against these pitches. Against sliders, Chourio has shown an even bigger improvement in squaring up these pitches, resulting in a 28.6% blast rate since May 9th.
Since minor league bat tracking data is not publically available, it is impossible to determine whether this has been an improvement or if Chourio has positively regressed to the squared-up ability he possessed during his time in the minor leagues. Regardless, this improved squared-up ability can likely be attributed to Chourio becoming more familiar with major league pitching as the season progressed. Perhaps an area of future research will be to see if recently-promoted hitters struggle with consistently squaring the ball up, or if this is a phenomenon that is exclusive to Chourio. Combining an improved ability to make contact with increased contact efficiency has allowed Chourio to consistently hit the ball harder, raising his overall level of production, and allowing him to come closer to reaching his offensive potential.
Moving Forward
By closing up a hole against four-seamers located on the outer third of the strike zone and improving his ability to square up his batted balls, Jackson Chourio has been able to reclaim his potential as a franchise cornerstone for the Milwaukee Brewers. Projection systems that Chourio likely will finish his rookie season with at least 20 home runs and 20 stolen bases, a solid debut showing for a prospect with touted power-speed upside. While I was correct in my initial analysis of Chourio that it would be foolish to write off his potential as a 30-30 threat, I was certainly incorrect to immediately lower his projection to a perennial 2-2.5 WAR player.
Perhaps I minimized the effects of age-to-level and expected him to perform too quickly, as Chourio is only 20 (!) years old which inheirtely means that there will be an adjustment period upon promotion to the major leagues. Given Blake Perkins’s presence in center field, I believe that I also placed too much emphasis on the fact that Chourio was looking like a corner outfielder with hit-tool struggles, raising concerns that he would not be able to meet the higher offensive bar of a corner spot due to the lower defensive value of the position.
Hopefully, this provides a lesson to not draw conclusions and/or dramatically revise future projections due to a slow five-week start to a major league career. If Chourio moves back to center field in the near future, then he may be destined for superstardom if he can combine his offensive improvements with plus defense. In conclusion, Jackson Chourio has made some significant changes to his offensive approach throughout the season, and projects to be one of the best young outfielders in all of Major League Baseball.
Photos by Icon Sports Wire | Adapted by Carlos Leano