The Royals and their platoon disadvantage

No rotation held the platoon advantage less in 2021 than the Royals. Their left-handers especially paid the price.

On May 3, when left-hander Daniel Lynch made his major league debut, the first hitter he faced was Cleveland’s César Hernández. Hernández, a switch hitter, naturally hit from the right side of the plate when greeting the southpaw Lynch to the bigs. He was the first of four consecutive batters to stand in against Lynch that evening from the right side of the plate.

In that game against Cleveland, Lynch faced a total of 21 batters. Four of them—Eddie Rosario and Josh Naylor two times each—hit from the left side, rarely affording Lynch the platoon advantage. The rookie exited after allowing three runs on four hits (and four walks) in 4.2 innings.

By the time Lynch came up against Cleveland again, this time at the end of the year in September, their roster had turned over quite a bit. The left-handed bats he faced in his debut were gone. Rosario had been dealt to Atlanta. Naylor was on the IL with a terrible leg injury. This time, the only left-handed bat in the lineup was Bradley Zimmer. Of the 25 batters Lynch faced that night, only three (all Zimmer) hit from the left side.

This was a scenario that played out all summer long in 2021 for the Royals and their left-handed starters.

• When Kris Bubic made a start against the Chicago White Sox on July 28, there wasn’t a single left-handed bat in the lineup.

• When Mike Minor made a start against the Detroit Tigers on May 21, there wasn’t a single left-handed bat in the lineup.

• When Danny Duffy made a start against the Minnesota Twins on July 3, there were two left-handed bats in the lineup.

The platoon advantage for pitchers happens when they face a batter of the same hand. We’ve all watched enough baseball to understand what that means. Playing the platoon advantage against a left-handed starter is good practice…something teams routinely attempt to do every time they come up against one on the schedule. According to FanGraphs, historically when a hitter holds the platoon advantage, his OPS is more than 80 points higher on average than when he faces a pitcher throwing from the same side.

Because the majority of hitters—and pitchers—in baseball ply their trade from the right side, left-handed pitchers often find themselves at a platoon disadvantage. In 2021, southpaws saw themselves face right-handed batters almost 72 percent of the time. Another way to phrase that is left-handed pitchers held the platoon advantage of facing a same-sided hitter just 28 percent of the time. It’s the bane of the southpaw existence. Especially when compared to their right-handed pitching counterparts.

Last summer, the Royals southpaws felt this more acutely than most lefties. This is the percentage of pitchers who threw at least 60 innings in 2021 and had the lowest platoon advantages (Ptn%).

That’s quite a list to have three Royals out of the bottom four.

The Royals had 76 starts made by left-handed pitchers in 2021. They had just under 100 innings thrown from lefties out of the bullpen. This is how the Royals’ overall platoon advantages stacked up against those Major League averages in the table above.

When the Royals had a right-handed pitcher on the mound in 2021, their platoon advantage ran right alongside the major league averages. But when there was a left-hander on the bump…They were way behind. By quite a bit.

Going back to the game examples I listed for each starter earlier in the article, you’ll recall that each opponent was in the AL Central. Chicago and Detroit were extreme right-handed hitting teams in 2021. Cleveland was right there, with Minnesota a little less righty heavy, but not by much. With the unbalanced schedule, this helped skew platoon advantage numbers that you see above. The Royals’ rotation suffered from geography and paid the price.

Let’s break it down a little more and see how each left-handed starter did by their platoon splits. The sOPS+ is the pitcher’s OPS+ against the split. If the number is above 100, they were that much worse, percentage-wise than the league average. Below 100, they were that much better.

Lynch had the platoon advantage only 12 percent of the time, the lowest among pitchers with at least 60 innings. That’s too bad, because that slider was nails against same-side hitters—and he was generally outstanding against batters up there from the same side. He threw the slider in 40 percent of offerings to left-handed bats and got a swing and a miss on the pitch almost 20 percent of the time. He just lacked opportunity.

The slider was still effective against right-handed bats (a .188 batting average against and a .266 slugging), but he threw it less against them.

When Lynch threw a four-seamer or change to right-handed batters…duck. Opposing righties crushed the change to the tune of a .368 BA and a whopping .658 SLG. They lit up the heater with a .381 BA and .575 SLG.

The wily veteran of the staff had a slight platoon split that favored right-handed bats, but it was certainly something that the club could live with while it navigated through the AL Central.

How about a left-on-left curve?

The numbers above for Minor in 2021 mirror his career stats. He has a very slight platoon split overall.

Bubic strangely had reverse platoon splits, where lefty bats did more damage than those from the right. The culprit was inexplicably his change up. Left-handed batters hit the Bubic change for a .321 batting average while slugging .786. Yeah…I triple-checked that slugging. It’s legit.

However, when that change was on, it was a thing of beauty.

But too often, he’d leave the pitch in the fat part of the zone. That would come with disastrous results.

Maybe that’s not exactly fair. I mean…Ohtani. Still, location matters and if Bubic is going to leave a change sitting there, it’s going to get destroyed more often than not. No matter which side of the plate the opposing batter stands.

Duffy was gnar, no matter where the batters stood, in 2021. It’s really a shame his season was short-circuited by injury.

Duffy wasn’t on the list above of left-handers with the most extreme platoon disadvantage but was close. He held the platoon advantage only 19 percent of the time in 2021.

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The platoon disadvantage isn’t the singular reason starters like Lynch and Bubic struggled in 2021. The issues were myriad, but it certainly didn’t help. Collectively, Royals’ southpaws had an sOPS+ of 92 against left-handed batters meaning they were eight percent worse in that situation than the league average. There were several left-handed staffs worse, including the Tigers (91 sOPS+) and the White Sox (88 sOPS+).

Still, the platoon disadvantage for their southpaws is a riddle the Royals will have to figure out how to solve—or at the very least improve. Looking at the very preliminary lineups for the upcoming season (whenever that starts), the White Sox will continue to skew very heavily to the right side. The Twins look to be the Central rival that has the most left-handed bats in their lineup on the regular. The Tigers added Tucker Barnhart who hits from the left side, but he could be given a rest for the right-handed hitting Eric Haase. The New Guardians lineup looks a little light for the moment, with plenty of platoon options. They could easily send out a lineup with eight or nine right-handed bats.

Of course, with a number of free agents frozen in lockout purgatory, some of these lineups will continue to churn. It’s not as if the Royals’ rivals in the Central decided to lean to the right on the lineups to stymie their pitching specifically. That’s just how the rosters break at this moment in time. But a true balance isn’t coming and clubs will continue to deploy right-handed bats against left-handed pitching.

The Royals themselves will figure to get fewer innings from southpaws in 2022, by the absence of Duffy. But given how he pitched last year, that’s not exactly a solution to the platoon advantage problem. And with Asa Lacy moving through the pipeline, the Royals will soon have another heralded—and key—left-handed pitching prospect they will have to break into the majors.

How their young southpaws learn to handle the AL Central lineups that tilt heavily to the right will go a long way to determining the success of the franchise in the next couple of seasons.