In 2018, Jesus Aguilar was given his first extended opportunity as a starting first baseman at the MLB level. He immediately broke out, posting an excellent .274/.352/.539 slash line with a 134 wRC+. Aguilar smashed 35 dingers, earning an All-Star game appearance and the top seed in the Home Run Derby. Coupled with unspectacular-but-solid defense at first base (+6 DRS, +1 OAA, +1.1 UZR/150), the slugger was worth 3.2 Wins Above Replacement according to Baseball-Reference.
While his breakout campaign was always likely to be the pinnacle of his career, the 16th-place NL MVP finisher looked like a legitimately solid first baseman moving forward. His underlying batted ball stats were strong: a 42.6% hard contact rate, an 11.4% barrel rate, and a .358 xwOBA, all of which placed him in the top 23 percent of qualified hitters or higher. For old-school fans, his smooth and effortless power stroke satisfied the eye test. Furthermore, Zeus’s plate discipline improved. He cut his strikeout rate down to a manageable 25.3%, and he drew walks at a 10.2% clip.
Unfortunately, the late bloomer followed up the best season of his career with his worst. A slow start cost him his starting gig — and eventually his roster spot — in Milwaukee. After a mid-season trade to the Tampa Bay Rays, he concluded the 2019 season with an underwhelming 88 wRC+ and just 12 home runs. The Rays designated Aguilar for assignment in November, and the Miami Marlins decided to take a shot on him.
Jesus figures to get consistent playing time — albeit in a shortened 60-game season — in Miami. It’s the perfect landing spot for someone who could use a low-pressure environment to reestablish himself. Is Jesus Aguilar simply a one-year wonder, destined to fade quickly into obscurity, or is the slugger who took the league by storm just two years ago still there?
Let’s start with the positive news. While Aguilar’s output in 2019 was a substantial step back from his All-Star campaign, his plate discipline improved. He further reduced his strikeout rate down to 22%, his swinging strike rate to 10.7%, and his chase rate to 29.8%. His walk rate increased to 11.7%. All of those marks were career-bests.
Now comes the bad news. Aguilar made more contact in 2019, but it was not the same kind of contact that he made the year prior. His average exit velocity was nearly identical to his breakout season, but his hard contact rate fell from 42.6% to 37.7%. Most concerningly, his barrel rate dropped from 11.4% to 7.5%. Hard contact was up across the league last season due to the juiced ball, making these individual trends even more worrisome. Aguilar’s fly ball and line drive rates both decreased by about three percentage points. Those well-struck balls were replaced by grounders (a career-worst 42.1% ground ball rate, compared to 35.4% the previous season). Ground balls are especially bad for someone like Jesus Aguilar, who has a sprint speed in the bottom 6% of the league. He’s not going to leg out any infield hits. As a result, his BABIP dropped from .309 to .272.
Digging deeper into the numbers reveals that the former 30-home run hitter got away from two things that made him successful in 2018: pulling the ball in the air and doing damage on fastballs.
Make no mistake, crushing the ball to all fields is what made the formidable power threat hard to beat in 2018 (his home run spray chart was actually quite balanced). If you pitched him outside, he would extend his arms and effortlessly drive the ball to deep right. However, some of his most prodigious power displays occurred when Aguilar would pull his hands in on an inside fastball and smoke it into the left field bleachers. For example:
In 2019, Aguilar’s overall pull rate fell from 43.5% to 37.1%. According to Statcast, pulled fly balls or line drives accounted for 22% of All-Star Aguilar’s contact, compared to just 14.6% in 2019. All-Star Aguilar slugged .602 and posted a .424 wOBA against fastballs; the following season, he only managed a pedestrian .403 slugging percentage and .329 wOBA against them.
2019 Aguilar strayed far from his usual profile. Whether it was intentional or not, he more closely resembled someone trying to slap singles and doubles than a true power hitter.
Let’s take a break from the numbers for a minute to look at some visuals. Here is Aguilar’s stance from June of 2018, at which point in time he led the National League in home runs:
As the pitcher began his windup, Aguilar’s legs were parallel to each other, he was standing upright with a slight bend in his knees, and his bat was resting on his shoulder. He kept this same stance for the entirety of the season.
In 2019, though, Aguilar cycled through three noticeably modified versions of his batting stance. The first major change came at the end of April. Aguilar and Brewers hitting coach Andy Haines were working hard to get him going, and this is what they came up with:
This was not a significant overhaul, but, notably, he was no longer resting his bat on his shoulder. He previously lifted it to this position when loading up, but holding the bat there to begin with eliminated some pre-swing movement. The big man smacked his first two home runs of the season in this game but failed to build much momentum beyond that.
By early July, Aguilar had once again altered his stance.
This is the first time that multiple changes in his setup were evident. He had much more bend in his knees and was not standing quite as upright as he used to. He returned to resting the bat on his shoulder, and his hands appeared to be slightly lower than they were in 2018. Perhaps the most discernable change was that he began using a much more open stance.
Fast forward to August, after Aguilar was shipped to the Rays. He appeared to have moved on to a middle ground between the parallel and open variations of his starting position.
It’s not uncommon for hitters to make tweaks to their batting stance, but the fact that Aguilar shuffled through multiple versions of his after sticking to one position the year before hints that he never truly felt comfortable in the box. As his struggles continued throughout the year, he was likely receiving numerous suggestions from various sources. Perhaps he overcorrected in an effort to get himself back on track.
There is evidence that positive regression alone will help Aguilar moving forward. He had a .307 wOBA, but his xwOBA was .334. He also finished the season with a 97 DRC+ (a stat that holds much more predictive power than xwOBA). These metrics indicate that he performed more like a league-average hitter than a below-average one.
Such a version of Aguilar would find himself signing minor-league contracts most winters and fighting for roster spots as a platoon bat. To be a quality regular once again, he will need to rediscover himself.
The first step is feeling comfortable with his stance and sticking to it. The Brewers counted on Aguilar to anchor the middle of their lineup. As a contending team, their patience with him could only last so long. The pressure to get going quickly may have contributed to his willingness to alter his setup numerous times. Now with a rebuilding team, the former All-Star has a longer leash, and he can afford to wait longer for results.
With his comfort level restored and his mind reset, Aguilar must focus on the approach that brought him success previously. If he can refine that approach, it is likely to work again. Opposing pitchers did attack Zeus with more high fastballs and threw fewer down-and-in heaters, but he still got a healthy serving of the pitches that he used to turn around into the seats. He simply stopped pulling them over the fence or for extra-base hits.
Due to the spread of COVID-19 and failed negotiations over the resumption of play, the 2020 MLB schedule is only 60 games long. Given the unpredictable nature of the current pandemic, there is no guarantee that MLB will play any games, and Aguilar could very well miss most of the season if he is infected by the virus.
For this reason, the upcoming season will not be a true bounce-back campaign for Aguilar. The sample size will not be large enough to prove for certain that he has returned to form, but it will be large enough to show that he is making progress. Even with abnormal circumstances, this summer is still an important one for his career trajectory. A batting line hovering around the league average without much power may result in a non-tender. Any opportunities in 2021 would likely come in the form of a non-roster invite or a move overseas. A performance closer to his career year — or even his solid rookie season — could result in a trade to a contending team or a long-term role in Miami.
Aguilar has a career 126 wRC+ in over 4,020 minor-league plate appearances and a 111 wRC+ across 1,310 in the majors. In his worst big-league season, his underlying metrics were still league-average. He is in a much better position than his former teammate Travis Shaw, who completely collapsed at the plate last year. Chances are high that Jesus Aguilar’s ability to be a solid offensive player is still there. A low-pressure environment to reset himself is what he needs most, and fortunately, that is exactly what he has.
Statistics courtesy of FanGraphs, Baseball-Reference, Baseball Savant, and Baseball Prospectus.