Going Deep: Using The Swinging Strike to Find Hitters Who Could Surge in The Second Half

Tim Jackson examines five hitters who could have big second halves based on recent drops in their swinging strike percentage.

We have a tendency to seek out stats like WAR and wOBA when it comes to evaluating a player because they’re more complex than any single stat. They take in and account for more data points, but also still spit out one nice number for us to dive into. It can be a neat little combination that hits a sweet spot of relative depth and ease. But the more moving parts that go into an intricate stat like WAR or wOBA, the longer they take to buy into. Sometimes that makes it harder to see things as they happen. 

When it comes to examining just one idea, with one stat, we get immediate feedback on a question right away without having to effectively do a background check on a bunch of individual components. We’re left with a kick-off point instead of a checklist. 

The swinging strike may tell us a little bit about some possible player turnarounds that started to happen before the All-Star break. If they continue, they could have a big impact on how things play out around the league down the stretch. Considering a player’s drop in whiffs and pairing it with a peek at their heat maps can give us a sense of their change in approach. Here are five guys who have had the biggest drop in swinging strikes over the last month’s worth of games before the break.

Player SwStr% through June 6 SwStr% after June 6 Difference
Brandon Lowe 20.1 14.6 5.5
Jesus Aguilar 13 7.9 5.1
Luis Rengifo 12 6.9 5.1
Manny Machado 12.5 8 4.5
Bryce Harper 16 12.2 3.8

Keep in mind here that the league average for swinging strikes this year is 11.1%. It’s jumped between two and four percent annually for the last five years as pitchers and hitters alike have optimized for the best possible outcomes. And this group represents a wildly varied kind of player. 


Brandon Lowe


Brandon Lowe’s drop in swinging strikes is something of a curiosity. He was supposed to be good, but not good in the way he has been in 2019. He’s been the third-best rookie behind only Pete Alonso and Fernando Tatis, Jr. and it has come by way of selling out big-time for power. He has the second-highest strikeout percentage in the entire league. 



But he’s worth keeping an eye on in the second half because if he’s more attuned to which pitches to swing at and at which to let go, he might have a chance to retain the power gains he’s made this year while being a more diverse threat at the plate. He’s been swinging less at pitches on the outer third of the plate and focusing more on when pitchers try to bust him inside. He’s still swinging and missing at a rate worse than league-average, so his profile may continue to carry volatility if he can’t settle in. 


Jesus Aguilar


After bursting onto the scene last season by bopping 35 homers and posting 3.5 fWAR, Jesus Aguilar has been a massive disappointment this year. He’s been a net negative for the Brewers and his playing time has accordingly dropped as the team tries to scrap ahead of the pack in a dogfight of a division. 



His swinging-strike rate for the year, whether considering his overall 11.8% or his 13% rate through June 6, isn’t terribly far off the 12.4% he worked with last year in his breakout. If he’s made a tweak, it appears to be in letting the stuff up in the zone go by and targeting what comes low and inside. That makes plenty of sense for a power-driven hitter like him, and it’s this kind of focus that may make him the biggest wild card in this entire group. Do the Brewers buy into what they’re seeing and find playing time for him, even though Eric Thames has been playing well, too? Do they platoon them? Does he get traded away to a team that will let him play even if he struggles? The next few weeks could determine a lot about the final line for Aguilar.


Luis Rengifo


David Fletcher, Tommy LaStella, Luis Rengifo. Do the Angels seem to have a type, or what? All of these guys are benefitting from a contact-heavy approach that is being especially rewarded by the way the new juiced ball is flying.

Throughout his time in the minors, Rengifo regularly banked double-digit walk rates and had strikeout rates that were rarely ever higher. Now he might be working toward that in the big leagues as he adjusts. Before the last month of play, he appeared fixated at going only at pitches in the middle third of the plate. It limited his ability to do damage in other zones and possibly even where he was swinging, as he may have been pressing to make the most of every piece of contact. Now he’s willing to dip slightly below the zone and even rip pitches inside when batting left-handed. 

With the same ball in AAA this year, Rengifo also had his highest career ISO at .191. Though it came in just 27 games at that level, we might see more of the same power as he settles into the Angels lineup. As a guy who can play multiple positions and get on base, he could meet a ton of upside in the second half.


Manny Machado 


The way Manny Machado is swinging and missing so much less right now might quietly be telling us about his continued progression as a player. His career swinging strike rate sits at 9.5%; his 12.5% rate through the first week of June tells us that he, too, was likely pressing after his standoff in free agency and finally signing his $300 million contract with the Padres. It’s easy to understand that a player of such renown and profile would immediately want to show everyone he is worth his contract, and maybe more.



But now, his swinging strike rate has swung an almost equal amount relative to his career number, except in the opposite direction. He’s worrying less about trying to catch everything inside and appears to have made a concerted effort to instead cover more of the plate away. His first half was frustrating to watch at times, but he’s still the same “set it and forget it” player who has absolutely hit his stride and may be finding a new level, as shown by his 158 wRC+ over the last month. With the way things are going in the NL for the wild cards a continued surge by Machado in the second half could be a big deal for the Padres and plenty of others. 


Bryce Harper


Bryce Harper, the other free agent darling of the winter, is the only other player on this list aside from Brandon Lowe who has cut his swinging strikes so much but still remains worse than league average. The good thing is that he’s trending toward his career number of 11.8%. Oddly, he’s offering at more pitches up and in and more pitches down and away since the first week of June than he was before then. The difference is that he’s making his contact count more, too, and handling stuff that was beating him earlier on. 



Over the last month, he’s been what the Phillies have needed, with five dingers, another three extra-base hits, and 20 walks. At this point in his career we probably should accept how he’s prone to wild peaks and valleys. But given that his first half was so low, his drop in swinging strikes could suggest that we’re in for one of those exhilarating runs from Harper that jolt his overall numbers as he pops off. The trick may be continuing to swing less but offering consistently at the pitches he can more easily drive. 

We have a few themes throughout the performances of these five players: Pressing, adjusting to new environments, and jostling for playing time. No matter the context for each individual, though, they could all separately be making conscientious adjustments that are telling us to keep believing or further invest. The swinging strike is just a single stat, but sometimes that’s the kind of help we need to see the big picture. 

(Photo by Cliff Welch/Icon Sportswire)

Tim Jackson

Tim Jackson is a writer and educator who loves pitching duels. Find him in the PL Discord, editing, managing, and podcasting with @BREAKINGPodPL here or writing at Baseball Prospectus.

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