Fluke or Breakout: Is Cedric Mullins’ 2021 Success Sustainable?

There might not have been a bigger surprise performer in 2021 than Cedric Mullins. With just over 400 plate appearances spread across parts of three years prior, he had put up a cumulative 72 wRC+ and accumulated -0.4 WAR; this season, he pushed his wRC+ up to 136 and posted 5.3 WAR, the 14th highest mark among all position players. He also became just the 11th player to reach 30 home runs and 30 stolen bases in a single season over the last decade.

The catalyst for his breakout season was quite simple: Mullins quit switch-hitting and began batting exclusively from the left side. That discussion had begun all the way back in 2018, his debut season, when then-Orioles manager Buck Showalter suggested it to him. After struggling to establish himself in the majors for three seasons, he finally decided to rely on his natural swing during the offseason. “It was getting difficult to try and create two different swings,” he told MASN’s Steve Melewski in March. “I know my left-side is my natural side, so trying to develop my right-handed swing at the highest level was challenging.”

Switch-hitting has always been a scarce skill, but the number of players who can swing both ways has dwindled in recent years. 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. But those previous examples were all players who had already established themselves in the majors. Mullins could have seriously damaged his chances of having a productive major league career if his decision went wrong.

Looking at his platoon splits, it’s clear he was struggling badly from the right side of the plate. During the first three seasons of his career, he posted an ugly .211 wOBA against left-handed pitchers as a right-handed hitter. His performance against right-handed pitching was much better, though still not great: a .303 wOBA, giving him a 92-point split. Under the hood, the difference becomes even more clear.

Even though he had accumulated just a handful of plate appearances against left-handed pitchers as a right-handed batter, it’s clear that his batted-ball and plate discipline peripherals were extremely poor. But his peripherals as a left-handed batter through the first three seasons of his career don’t indicate that an impending breakout was brewing.

One of the reasons why Mullins’ batted-ball data took such a dramatic turn for the better in 2021 was because he spent the offseason tinkering with his left-handed swing. Unburdened from maintaining two different swings, he focused on making his one more consistent. He described those changes to David Laurila in an August interview:

“If you put a side-by-side of my swing in 2019 versus now, the approach itself is relatively the same, but I’m standing a little more upright than I used to, [and] I have my barrel flatter as a starting point as opposed to more vertical. Those small adjustments helped make my swing more consistent, just more useful in games.”

Here’s those two versions of his swing, side-by-side:

Both changes Mullins pointed out in his interview are evident in that image above: he’s standing more upright in the box, and his bat is held parallel to the ground. His hand position, in particular, is much more engaged. With his old stance, there was a lot of movement with his hands to get them into a good position to swing. Now, they’re far more direct to the ball once he starts his swing.

Those tweaks he made to his swing certainly paid off. Looking back up at the table above, all of his batted-ball metrics significantly improved in 2021, as he set career highs in all of them. His batted-ball mix saw some noticeable gains, too:

During his first three years in the majors, Mullins was among the league leaders in pop-up rate. His flatter swing path helped him cut down on the amount of automatic outs he made on the infield and also decreased the number of ground balls he put in play. His sweet spot rate, which measures batted balls hit with a launch angle between eight and 32 degrees, increased from 23.4% to 35.1%. All that additional elevated contact at optimal launch angles resulted in an explosion of doubles and home runs.

His plate discipline splits didn’t noticeably improve as a left-handed hitter, but simply cutting out the poor swing decisions he was making as a right-handed hitter ensured his overall plate discipline metrics improved to career-bests as well. Because Mullins is naturally left-handed, giving up switch-hitting still allowed him to face the platoon advantage in the majority of his at-bats. While facing the platoon disadvantage for the first time in his career, he was surprisingly productive, posting a .339 wOBA against left-handed pitching in 2021, and his strikeout rate against southpaws was nearly the same as it was against righties.

With a dynamic skill set unlocked by his decision to quit swinging from the right side, Mullins quickly established himself as a key piece for the Orioles to build around. But can he repeat the success he enjoyed in 2021? Here’s his ZiPS projection broken down into various percentiles:

His 50th percentile projection (the projection that showed up in the Orioles ZiPS projections that ran last week) is good, but it would represent a pretty significant step back for him. A repeat of his breakout season would fall somewhere between his 80th and 90th percentile projection. With such a small sample to pull from as an exclusively left-handed hitter, the computer probably has a hard time reconciling his past struggles as a switch-hitter with his massive success this season. Some skepticism is probably warranted, but many of the improvements he made look like they should be sticky.