Swinging Less Is Better, At Least in the NL West

This year’s edition of baseball has produced some fascinating hitting performances. We’ve written a lot about Yasmani Grandal and his unprecedented batting line (a 134 wRC+ despite hitting .188). He’s done that in part by swinging at just 30.2% of pitches that he sees in ‘21, lowest in the majors by a wide margin. Max Muncy has also been incredibly selective, offering at just 35.4% pitches, the lowest rate of his career. These players have found that swinging less helps their game, but generally it’s not a trend that we’re seeing across the league. If anything, league-wide swing rates have increased (albeit marginally); this season’s 46.8 Swing% is the third highest since 2000. For every Muncy, there’s also a hitter who likes to swing at just about everything. Salvador Perez and Tim Anderson, for example, have swing rates of 60.3% and 59.3%, respectively.

The outliers are certainly interesting, but just how little can a big leaguer swing and still get away with it? What we’re talking about here are O-Swing% and Z-Swing%. By themselves, these are telling statistics, as hitters with a high O-Swing% strike out a lot more than those with a low O-Swing%.

For context, a 5% increase in O-Swing rate on average results in an increase of 1% to strikeout rate. This relationship is even stronger when it comes to drawing walks.

So far in ‘21, a 5% decrease in O-Swing rate on average results in an increase of 2% in walk rate.

I realize this is obvious and intuitive, but the impact of chasing pitches out of the zone is at the heart of plate discipline. We’re in the middle of the three true outcomes (TTO) era, after all, where drawing walks has never seemed more valuable. Being able to “take” a pitch is a learned skill, and some hitters are most definitely better than others at it. Here’s an example of a good take by Joe Panik:

This particular Brad Hand slider is perfectly placed — just outside the zone and working a 12-inch break starting inside the zone. With two strikes, few hitters will lay off this pitch. You can just catch Hand’s reaction after the pitch, too; it was exactly what he wanted to throw.

Hitters do still need to swing. They can’t just take all pitches, despite Devan Fink’s efforts to convince us this may be a good strategy against Jacob deGrom. But rather than indicate a hitter’s ability to refrain from chasing pitches out of the zone, a low O-Swing% is often just an artifact of a hitter who has a low swing rate at pitches in the zone as well. Muncy, for example, has the third lowest Z-Swing% (60.2) among qualified hitters. Juan Soto has a less extreme split, but his 64.1 Z-Swing% is still well below the league average of 68.4. Few hitters can pair an aggressive approach to the plate and a low propensity to chase. Kyle Tucker is one such hitter who is finding success at balancing these abilities. Per Kevin Goldstein’s recent take on Tucker in this year’s Trade Value series:

“His ability to avoid swinging at balls out of the zone is the same as ever, but he’s become far more aggressive within the zone, which when combined with one of the better hard hit rates in baseball and continually-improving power, has led to the breakout we’re starting to see.“

Since 2019, Tucker has been able to decrease his O-Swing%, bringing it below league average so far in ‘21. At the same time, he’s ratcheted up his Z-Swing% to 83.2, second highest among qualified hitters.

It’s a unique skillset. Tucker swings at pitches in the zone at a rate 52.4% higher compared to his out of the zone rate. If we take this difference (let’s call it D-Swing%) for hitters with at least 100 plate appearances, Tucker ranks second behind Brandon Belt.

One thing that jumps out: several Giants make the leaderboard, and as a team, they are second in D-Swing% behind only the Braves, largely backed by the third lowest O-Swing% in baseball (27.4%). The Giants are a veteran squad with several key position players aged 30 or above who are chasing at a rate well below their career averages, including Belt, Tauchman and Wilmer Flores.

Since 2019, the Giants have dropped their team O-Swing% from 33.7% (fifth highest) to 27.3% and seen their walk rate increase almost 3% in the process. This focused approach has helped them climb to fourth in all of baseball in walks (372) this season. The extra baserunners from all the walks have not been left stranded, either. As much as they like taking a free base, the Giants still let it rip at the plate, leading all teams in home runs with 144.

The NL West may very well be decided by the team that can most effectively capitalize on the benefits of minimizing their O-Swing%. Each of the Giants, Dodgers, and Padres land in the bottom five in baseball as a team for chase rate. Their offensive production looks quite similar in affected categories as a result:

While league-wide walk rates have held fairly stable, this trio of NL West teams may be pushing the TTO narrative even further. The Red Sox would have something to say about that; they have the highest team-wide O-Swing% at 34.7 and fourth lowest walk rate (7.7%), but that hasn’t gotten in the way of their offensive production, as they’ve scored 495 runs, third best in baseball. That said, the Red Sox, Dodgers, Padres, and Giants all have a better than 90% chance of making the playoffs per our latest playoff odds. We may just see these two approaches come to a head in October.