The search for Jesus Aguilar’s bat

Jesus Aguilar was a breakout star in 2018. Eric Thames injured his thumb and missed substantial time. Aguilar took over for him at first base and essentially Korea’s version of God got “Wally Pipp-ed.” Aguilar did not relinquish the job slashing .274/.352/.539 in 2018. His torrid first half resulted in an All-Star appearance and the understanding that he would be the “no doubt” starting first baseman for the Milwaukee Brewers.

Unfortunately, his second half of 2018 was not comparable to his first half. To illustrate, his 2018 first half slash line was.298/.373/.621. His second half slash was .245/.324/.436. Coming into 2019, there was a lot of talk about whether the big first baseman could get back to his first half self.

The early indications in 2019 suggest he might be more likely destined for the bench than another All-Star appearance. In fact, getting something more akin to what he was during the second half of 2018 would be an improvement. At the time of the writing of this article, Aguilar is slashing .148/.254/.185. He’s been dropped into the bottom half of the batting order. And most concerning is that his hard hit percentage for this year is just 30.2% as opposed to 42.6% in 2018. Obviously the man affectionately known as Zeus could go on a tear and change everything quickly. Yet it is cause for concern, and manager, Craig Counsell has to be considering more playing time for Eric Thames.

Trying to understand why Aguilar has gone from great to average to bad is frustrating. One way to attempt to understand is to discern areas of difference between when he was great and when he was not. Statistically a few things stand out. First half of 2018 version of Aguilar had a fly ball rate of 45.4%, ground ball rate of 30.6%, a pull percentage of 48%, a hard hit rate of 45.4%, and home run to fly ball rate of 27%. Compare that to his second half where his fly ball rate was 35.6%, his ground ball rate was 41.1%, his pull percentage was 38%, his hard hit rate was was 42.3%, and his home run to fly ball rate was 19%.

In Aguilar’s first 65 plate appearances of 2019, he is even worse, and it shows in more categories. So far, his hard hit rate is just 30.2% vs. 42.6% in 2018. When we compare first half 2018, second half 2018, and 2019, we see even more interesting results. His ISO — or isolated power — for 2019 is .037 compared to an ISO during the first half of 2018 at .324 and second half at .191. The first half of last year resulted in a BABIP of .331 vs second half of .283 vs. 2019 of .186. One more interesting thing is his strikeout percentage. He is striking out less in 2019 — 18.5% vs 25.3% in 2018. It seems he is unable to get the ball in the air. It might be the result, at least in 2019, of making more (but less substantial) contact. By the way, he has yet to hit a home run and has only two extra base hits.

Part of the reason Aguilar is having these problems is without a doubt because MLB pitchers have adjusted. My young colleague Jack Stern wrote about adjustments made by pitchers during the second half of 2018. According to Stern, opposing pitchers began throwing fastballs down in the zone more than they did in the first half, resulting in more balls on the ground and less in the air as well as less opportunity to pull the ball.

Every hitter that comes onto the scene successfully will have to adjust to the adjustments made to him. Jay Bruce, Yasiel Puig, and Cody Bellinger are just a few names that come to mind that performed extremely well during their first taste of opportunity. In all three cases, pitchers adjusted, and in all three cases the hitters struggled. Each has achieved differing degrees of success based on adjustments they made. Aguilar will have to do the same in order to remain as the Brewers’ starting first baseman.

Coming into this analysis, I thought he would need to take an up-the-middle to opposite field approach. I have observed him attempting this very thing recently. As with many hypotheses, this one does not hold up in the face of the data. The reason he would want to go up-the middle or the other way is to keep from rolling over when pulling outside pitches and grounding out to third or short. He does this quite a bit. It makes logical sense. Yet his hard hit rate is down even as his strikeout rate falls. He needs to drive pitches that he can hit as opposed to hitting pitches that the pitcher wants him to hit.

Based on the data results mentioned above, he may need to make a few changes. Now, I am merely a writer with some analysis skills. Zeus should listen to his coaches, fellow players, and his experience rather than me. But just in case he reads this, here are my suggestions:

1. Hunt mistakes up in the zone. Look for hanging breaking pitches and fastballs that miss their location. Become a hitter that crushes mistakes.
2. Become aggressive early in counts. Aguilar was one of the best two strike hitters in baseball last year. That success likely makes him reluctant to do this. However, hunting mistakes means focusing on a place in the zone and attacking pitches that come into it. He may have to attack early, at least for awhile, to get those pitches.
3. Become more selective. This seems counter-intuitive, but I am suggesting that he not swing at anything low in the zone. Pick a spot middle in or middle out that is just below the belt or above and attack with fervor when a pitch enters that area. Otherwise let the pitch go.
4. Spit on the slider away. Obviously that is easier said than done. Pitchers with great sliders make their living on that pitch. If he can pick up the proverbial dot of the slider, could he lay off that pitch?
5. Seek to drive the ball over making contact. I would be surprised if this isn’t the goal, but results suggest more contact over hard contact is the reality. That needs to change.

Carlos Pena offered insights on MLB Network not too long ago that summarize the approach I am outlining for Aguilar.

Jesus Aguilar was one of the reasons the Brewers won the NL Central in 2018. At this point in 2019, his contribution is more detrimental than positive. If it continues, Eric Thames might just take the job back. That said, it is hard not to pull for the 2018 breakout performer. As with Christian Yelich’s current level of play in the positive, Jesus Aguilar’s current level of play in the negative surely can’t be sustained? Look for more positive results soon.

Baseball statistics courtesy of Fangraphs and Baseball Savant