Finding Switch-Hitters Who Should Stop Switch-Hitting

Back in December, I wrote about Cedric Mullins’ breakout 2021 season, the catalyst for which was a decision to stop switch-hitting and begin batting exclusively from the left side of the plate. By dropping his right-handed swing, Mullins, a natural lefty, could focus on honing one swing instead of struggling to maintain two separate swings.

Switch-hitting has always been a rare skill throughout baseball history, but the number of batters who can swing both ways has dwindled in recent years. From that previous piece:

In 2021, just 17 qualified batters (13.1%) were switch-hitters, right in line with the league-wide average over the last decade. Compare that to the decade between 1986 and ’95 (excluding the strike-shortened 1994 season), when more than one in five qualified batters (21.1%) hit from both sides, with a peak of 24.8% in ’89. With modern baseball strategy so heavily emphasizing the platoon advantage, it’s surprising to see so few switch-hitters these days. Giving up that advantage in every at-bat is a radical decision, and there’s barely any precedent for it.

The number of players who have dropped switch-hitting after making their major league debuts is tiny. J.T. Snow did it in 1999, halfway through his career. So did Orlando Merced in 1996. Shane Victorino flip-flopped between switch-hitting and batting right-handed after injuries forced him to give up left-handed batting at various points during his career. More recently, Tucker Barnhart gave up switch-hitting in 2019.

After seeing the success Mullins had after giving up swinging from the right side, the obvious follow-up question is whether we can identify any other switch-hitters who might benefit from focusing on swinging from one side or the other.

The extremely small number of players who have actually made the decision to stop switch-hitting at the major league level should tell us that this isn’t a silver bullet solution to a player with a wide platoon split. Anecdotally, more players stop switch-hitting in the minors because they have a lot more to gain if the adjustment pays off. For those players who have already made it to the majors but haven’t truly established themselves, like Mullins, it’s a risky decision. They’d be making the change against the best the sport has to offer, likely resulting in a significant adjustment period. Still, with teams focused on finding every miniscule advantage to wring out of their rosters, it’s a worthwhile question to pursue.

Finding the players who might be candidates to stop switch hitting isn’t as simple as calculating the largest platoon splits. But just to set the sample parameters at their widest, I pulled all of the active switch-hitters who have accumulated at least 1,000 plate appearances during their career. The career platoon splits of the resulting 25 batters are shown below.

According to the authors of The Book, it takes around 600 plate appearances against left-handed pitching for the platoon split of a switch-hitter to stabilize. Even with a 1,000-plate appearance minimum, many of the players above haven’t reached that threshold yet.

This isn’t the first time this question has been asked. Back in 2014, Ben Lindbergh investigated this same question for Baseball Prospectus. In that article, he used a heavy regression model to calculate the estimated performance of a switch-hitter who decided to go one way. Using his method, four players appear to be good candidates to stop switch-hitting: Ozzie Albies, Ian Happ, Tommy Edman, and Ketel Marte.

Using a regression model to estimate performance is a blunt way of approaching the problem, though at the time, Lindbergh didn’t have access to the kind of granular batted ball data we do today (Statcast was one year away from implementation). For Mullins, I examined the handedness splits of some of his underlying metrics, and it quickly became clear that his batted-ball and plate discipline peripherals as a right-handed hitter were extremely poor. That alone should have convinced him to drop swinging from the right side, even if his peripherals as a left-handed batter weren’t much to sneeze at.

To dig further into the list of switch hitters above, I pulled handedness splits for those same key underlying metrics to see if any of them are potential candidates to make such a drastic change. Once I had the peripheral splits, I calculated z-scores based on the league standard deviation for each metric. The sum of those z-scores should tell us which batters under or over perform from one side of the plate in particular.

For reference, here’s what Mullins’s handedness splits and z-scores looked like heading into the 2021 season.

Simply pulling handedness splits and extrapolating from there won’t tell us exactly how these players will fare as single-sided batters, but eliminating severe underperformance from one side of the plate could be a path toward improvement. (That said, there’s no guarantee that the strong peripherals from the other side of the plate will translate well once the hitter is facing same-sided pitching.)

With all that preamble out of the way, let’s examine some specific cases.

Switch-hitters who should go left-handed full-time
The main benefit of switch-hitting is having the platoon advantage in every at-bat; giving up that edge should be a difficult decision. For switch-hitters who excel against right-handed pitching but struggle against lefties, that decision is made a little easier. They already perform well against the majority of pitchers they face, so deciding to bat left-handed full-time is a little less demanding. This was one of the reasons why Mullins’ transition was so successful.

Happ had the second-highest platoon split behind Albies, and like Mullins, he really struggled as a right-handed batter. His ability to swing with power is severely hampered, with his average exit velocity, barrel and hard-hit rates, and xwOBA on contact all more than a standard deviation below his career rates. His plate discipline metrics aren’t as bad as a righty, though, which tells me that something mechanical in his swing from that side is preventing him from making authoritative contact regularly. His cumulative z-score was the highest in our sample, almost as high as Mullins was as a switch-hitter. Lindbergh’s regression model sees Happ posting a .338 wOBA as a full-time left-handed batter, just a couple of points lower than his career wOBA of .342.

Moncada suffers from the same issues as Happ, though to a lesser degree. His wide platoon split haven’t gone unnoticed either. Back in 2018, his first full season in the majors, the question of batting left-handed full-time was at least considered. At the time, the coaching staff and Moncada decided it was too early in his career to call it quits on switch-hitting, but with three more years of bad performance against left-handed pitching behind him, it might be time to revisit the question.

Switch-hitters who should go right-handed full-time
For a switch-hitter to decide to bat right-handed full-time, the potential gains need to outweigh the substantial loss of the platoon advantage in the majority of their plate appearances. This makes this decision even more fraught with risk.

When discussing switch-hitters who should give up switch-hitting, Albies is usually the first name to come up. He sports an 80-point platoon split, the largest in our sample of hitters. It’s an issue he recognizes too: 12 of his plate appearances as a right-handed batter have come against a right-handed pitcher during his career, with eight of them in 2021, including two in the World Series against Zack Greinke. Half of those right-on-right plate appearances came against position players pitching, but he did decide to bat righty against Ryne Harper on two occasions last summer, hitting a home run in his second of those at-bats. In his postgame comments after that go-ahead homer, Albies said that Harper’s steady diet of offspeed pitches was the deciding factor. A lack of high-end velocity seems to be the common element among the pitchers he chooses to bat same-handed against: Harper’s fastball averaged 86.5 mph, and Greinke’s heater has sat below 90 mph for the last two seasons. None of the position players he faced were breaking 90 mph, either, and Albies also chose to bat right-handed against knuckleballer Steven Wright.

As far as his peripherals go, Albies doesn’t drastically diverge from his career averages as a left-handed batter. He isn’t able to hit for as much power against right-handed pitching, but his plate discipline is essentially unchanged. Regressing his platoon split if he were to go right-handed full-time produces a .319 wOBA, a significant step down from his .338 career mark. He’s probably better off picking and choosing which right-handed pitchers to give up the platoon advantage against like he did in 2021 instead of abandoning switch-hitting altogether.

Edman’s peripherals look similar to those of Albies; he’s useful against left-handed pitching and not that bad against right-handed pitching. His power numbers as a right-handed batter are encouraging, which could help him reach the lofty .196 ISO he sported in his rookie season, but as a contact-oriented hitter, he’s probably better off sticking with the platoon advantage in all of his plate appearances.

Even though Marte’s platoon split is large, his peripherals tell a different story. He definitely hits for more power as a right-handed batter. That swing comes naturally, allowing him to go after pitches he can punish. His left-handed swing requires a bit more maintenance and presence of mind to make sure his mechanics are all aligned. Complicating things even more, his plate discipline splits aren’t as pristine as a righty: He’s prone to chase pitches out of the zone more often, leading to a higher swinging-strike rate. His cumulative z-score is the lowest of the five batters we’ve examined.

…

What has this little exercise taught us? Nothing we probably didn’t know already. Mullins’ transition to a full-time left-handed batter was a risky but ultimately beneficial decision based on his underlying struggles as a right-handed batter. We could probably say the same about Happ and Moncada, since they’d be transitioning to swinging left-handed full-time as well. As for Albies, Edman, and Marte, the calculus is a little more complicated, since they’d be transitioning to right-handed batting full-time.

Albies might have the right approach, where he picks and chooses the right-handed pitchers to face as a righty so he can better leverage his strengths. But because Happ and Moncada are already established major leaguers, they have less of an incentive to make such a dramatic change. Mullins found the perfect combination of circumstances and skill to make his decision to stop switch-hitting a success.