Swing Rate and Rookie Hitters (And What It Means For 2023)

Fantasy draft season heating up, especially in dynasty and keeper leagues. As a result, fantasy managers are in the midst of determining which players are worth keeping long-term. And no kind of player is more polarizing than rookies who will be entering their sophomore seasons, especially those of the position player variety.

In this past season, fantasy baseball players and baseball fans, in general, were treated to a tremendous rookie class position players, which resulted in Seattle’s Julio Rodríguez and Atlanta’s Michael Harris II netting the American and National League Rookie of the Year honors, respectively. While Rodríguez and Harris earned top honors in their respective leagues, there was plenty of rookie-hitting talent that did not earn the award that could have in any other season. Adley Rutschman of Baltimore, Steven Kwan of Cleveland, and Bobby Witt Jr. of Kansas City made their cases in the American League, while Brendan Donovan of St. Louis was also a finalist in the National League. Fantasy managers who rostered any of those hitters above benefited from their production during the 2022 season.

Of course, a strong rookie season can only mean so much.

Angel Berroa won the Rookie of the Year award for the Royals in 2003 and ended up only generating a career bWAR of 1.0 over 746 career MLB games. Even last year, Akil Baddoo went from one of the better rookie stories in baseball in 2021 (110 wRC+) to a lackluster sophomore campaign that saw him going up and down between Detroit and Triple-A Toledo (65 wRC+). With this being known, which “soon-to-be” sophomore MLB hitters are due to either improve, continue to be consistent, or perhaps decline in 2023?

In order to figure that out, I decided to look at swing rate and contact data from 2022 and 2021 rookies to see if any interesting trend emerged that could help fantasy baseball managers and their decision-making for this upcoming offseason.

 

Why Swing Rates?

 

When glancing at the top-hitting rookie finalists from this past Rookie of the Year voting, it was interesting to see how varied their approaches were to success in 2022.

Here is a look at the top seven position player rookies from last season who either won or were in serious consideration for the Rookie of the Year award in their respective leagues.

The difference among their walk and strikeout rates, as well as BB/K ratio, particularly stood out.

Rutschman, Kwan, and Donovan all produced a solid BB/K ratio (0.75 or above) that correlated with their fWAR or offensive runs above average (Off). Rodríguez, Harris, Peña, and Witt on the other hand all were BELOW league average (0.36) in BB/K ratio. And yet, it didn’t seem to have that much of an impact on their offensive production.

That is especially true in Rodríguez’s case, as he produced the same fWAR as Rutschman, and produced 10 more runs on an offensive end, despite producing a BB/K ratio that was 0.48 points lower than the Orioles’ rookie catcher. Intrigued by these discrepancies, I took a deeper dive into the actual approaches of these rookie hitters, especially ones who produced above-average value on an fWAR end. Walk and strikeout data only told so much of the story, unfortunately. Analyzing swing data, particularly on the O-swing (swings outside the strike zone), contact, and swinging strike rate end made the most sense.

By taking a look at rookie hitters’ swing and contact data, some trends could emerge that could signify whether those low BB/K ratio rookies could improve in 2023, or instead hit a wall due to their deficiencies being masked by batted ball luck in 2022.

 

Rookie Hitter Swing Rate Data (2022)

 

As a baseline, I decided to only look at rookies from 2022 who produced an fWAR of 1.0 or higher. That did leave some of the more popular names off this list, including Joey Bart, Riley Greene, CJ Abrams, MJ Melendez, and Spencer Torkelson.

However, it was important to see which rookies actually had a POSITIVE impact on their squads in 2022. Therefore, the 1.0 fWAR or higher baseline seemed to make the most sense.

Here’s a look at those rookie position player producers, as their fWAR data is included in the table below along with traditional metrics that are used in typical 5×5 leagues (average; home runs; runs; RBI; and stolen bases).

The only real rookie who had a case that he was snubbed in Rookie of the Year voting may be Nootbar, though his .227 batting average probably weighed down his candidacy among traditional BBWAA voters.

Now of that group, let’s take a look at the swing data, with the primary categories being swing rate, O-Swing rate, contact rate, swinging-strike rate, and wRC+. The group is ranked by swing rate, so those with the highest swing rates are at the top of the group.

The MLB average swing rate was 47.7 percent, which means 13 rookies last year swung more than average. Of that group of 13, three hitters produced below-average wRC+ marks (Witt, Siri, and Rivera). On the flip side, of those who ranked 14th to 23rd (i.e. below league average in swing rate), only one was below that average 100 wRC+ mark (Bryson Stott of the Phillies at 85).

Granted, two hitters (Fortes and Suwinski) were exactly league average, so one could argue that the swing rate data didn’t necessarily produce any defining differences among this rookie group of hitters.

It is interesting though if you compare the five hitters with the highest swing rates (Gonzalez, Peña, Zavala, Harris, and Cabrera) and those five hitters with the lowest swing rates (Rutschman, Suziki, Nootbar, Donovan, and Kwan), especially on a wRC+ end.

• Average wRC+ of Top-5 swing rate hitters: 116.4.
• Average wRC+ of Bottom-5 swing rate hitters: 125.4.

Those core five hitters who didn’t swing often actually produced an average wRC+ that was nine points better than that group of hitters who frequently swung higher than average.

If we expand the sample to all hitters who swung above average, and those who swung below the average rate of this sample, these are the results we see:

• Average wRC+ of hitters above the league average swing rate: 114.9.
• Average wRC+ of hitters below the league average swing rate: 115.3.

While not as pronounced, hitters who swung less overall from this rookie class tended to have more success than those who swung more, with the exception of Rookie of the Year winners.

 

Rookie Hitter Swing Rate Data (2021)

 

In order to get a better idea of this past rookie hitter class’ production and how swing rates connect, it seemed sensible to compare rookie hitters from the 2021 season.

Here’s a look at all rookie hitters in 2021 who produced an fWAR of 1 or higher.

In 2021, the league average swing rate was 47.2 percent. Hitters ranked 1st through 12th had higher than average swing rates, while 13th-25th generated lower than league average rates.

Of this particular group, those who swung more tended to struggle a lot more, especially in comparison to their 2022 rookie counterparts.

Of hitters ranked 1st through 12th, five posted below-average wRC+ marks, which included Adolis García (99), Brendan Rodgers (99), Daulton Varsho (99), and Jonah Heim (60).

On the flip side, of hitters who ranked 13th through 25th in swing rate, only  Jazz Chisholm Jr. (97), Ke’Bryan Hayes (87), and Sergio Alcántara (73) posted wRC+ marks under 100.

Let’s also take a look at the top five and bottom five swing rate groups from this 2021 rookie class:

• Average wRC+ of Top-5 swing rate hitters: 112.4.
• Average wRC+ of Bottom-5 swing rate hitters: 102.

Surprisingly, the most frequent swingers actually out-produced the most patient rookie hitters in 2021, and by a 10-point margin to boot. It’s pretty much the inverse of what we saw from rookie hitters in 2022, at least in this sample.

Here are the results when we expand the sample to include all rookie hitters:

• Average wRC+ of hitters above the league average swing rate: 107.2.
• Average wRC+ of hitters below the league average swing rate: 107.3.

More patient rookie hitters overall barely edged out aggressive rookie hitters in 2021, similar to 2022. That said, the gap was much smaller (0.1 to 0.4 in 2022).

 

How Did They Do As Sophomores in 2022?

 

My next step in this process was to see how those 2021 rookies fared in their sophomore seasons last year. Did their approaches change? And did those free-swinging hitters perhaps get more exposed in their second seasons at the MLB level?

Here’s a look at the swing data from that 2021 rookie group, but this time, in 2022.

Hitters ranked 1st through 14th produced higher than league-average swing rates (47.7 percent). Here is how the results fared for this sophomore group of hitters:

• Average wRC+ of hitters above the league average swing rate: 100.6.
• Average wRC+ of hitters below the league average swing rate: 94.3.

Not only did free-swinging hitters once again out-produce patient ones, but this time the gap widened. After a 0.1 advantage for patient batters in 2021, the gap switched to 6.3 points last season in favor of aggressive ones.

 

Digging Into Contact Rate and BABIP

 

To get more perspective, I created a table that highlighted those sophomore hitters’ differences in swing rate, contact rate, BABIP, and wRC+ from 2021 to 2022.

It seemed sensible to organize this group of hitters primarily by wRC+ in order to highlight hitters who improved upon their rookie seasons to those who declined last season after promising rookie debuts.

The difference that correlated the most with wRC+ success for hitters in their sophomore season was contact rate improvement from 2021 to 2022.

Of the eight hitters who saw positive gains in wRC+ in 2022, six demonstrated growth in making contact. This proved to be a much stronger correlation than either swing rate or BABIP, which each only had four instances of improvement from that group of eight. The only exceptions to the contact improvement rule were Jazz Chisholm Jr. (who saw a 2.7 percent decrease) and Daulton Varsho (who saw a one percent regression). Surprisingly, Chisholm improved the most in wRC+ from 2021 to 2022 of that particular group of players, which probably speaks to his batted ball quality (he did nearly double his barrel rate from 2021). Thus, it’ll be interesting to see how his 2023 season fares, especially after his second half was so marred by injury. On the other hand, making more contact didn’t always guarantee better results in 2022.

Of the bottom ten hitters of this sophomore group, six saw improvements in contact rates from their rookie seasons. This includes big names such as Baddoo (2.4 percent), Dylan Carlson (2.9 percent), and Patrick Wisdom (4.8 percent). And yet, despite that positive increase, all saw double-digit declines in wRC+ in their sophomore seasons at the MLB level.

 

What Can We Take Away? (And Apply To This 2022 Rookie Class?)

 

There can be a tendency to think that hitters who swing more than average will automatically be susceptible to negative regression the following season. The 2022 rookie class has some free-swinging hitters, with Rodríguez, Peña, and Witt being the most prominent examples. On the other hand, the 2021 rookie class proved that “patience” doesn’t always lead to success. Last year, more patient sophomore hitters underperformed more aggressive hitters by nearly 6.5 points in wRC+. That gap cannot be ignored, especially by fantasy baseball managers looking for young hitters they can build their roster around in 2023 (or beyond in dynasty and keeper leagues).

It may be easy to see the free-swinging tendencies of Witt, Peña, or Rodríguez and think that they may be worth trading this offseason for more established commodities or exorbitant packages. But the data shows that there is not only still hope that those kinds of hitters can continue to improve in 2023, but that they could produce even greater results.

Robert Orr of Baseball Prospectus looked at Rodríguez, Witt, and Peña’s improvement in contact rate at the midpoint of last year. Orr pointed out they were already making improvements in hitting balls in the zone, despite the high frequency of swings.

.@NotTheBobbyOrr checked on three of the biggest AL Rookie names this week in Julio Rodríguez, Bobby Witt Jr., and Jeremy Peña and broke down their adjustments since arriving in the majors:https://t.co/vFD9pkAAcf pic.twitter.com/0MNgZnNaWM

— Marchioness of Craigmondeley (@cdgoldstein) July 1, 2022

Orr’s observations can correlate with aggressive swingers from the 2021 rookie class, as they eventually made adjustments in contact ability in 2022. Of the group of hitters who saw declines in swing rate from 2021 to 2022, their contact rate difference over that two-year span was 0.3 percent. As for the more free-swinging ones? Their difference was 1.1 percent. Safe to say, it’s likely that free-swinging hitters like Rodríguez, Peña, Witt, and even Harris will see improvement in contact rate in 2023, even if their 2022 rates weren’t impressive (Rodríguez: 71.2 percent; Peña: 71.4 percent; Witt: 77.6 percent; Harris: 73.5 percent). Rookie hitters come with all kinds of questions and concerns, even after they prove (or disprove) themselves in their MLB debut season. Nonetheless, the 2021 rookie class proved that a free-swinging approach isn’t necessarily a “death knell” for a hitter’s outlook the following season. These types of players should still be viewed as cornerstones of a fantasy roster.

And for those with hitters who had low swing rates?

Well, some regression could be coming their way, as the 2021 rookie hitter data demonstrated.

If anything, those may be the hitters that fantasy managers should probably be exploring trades for this offseason in dynasty or keeper leagues, not the free-swinging ones, as many may have thought initially (including myself).

 

Feature image by Michael Packard (@CollectingPack on Twitter) / Photography by John McCoy & Brian Rothmuller/ Icon Sportswire