Reasons why right-handed power has become rare

Right-handed power. It’s the buzzword — or perhaps the buzzphrase — of the offseason. Every day, we wake up to news of another team throwing big money at a free agent because he has some history of strong offensive performances and he bats from the right side of the plate. There was $88 million for Hanley Ramirez, $57 million for Nelson Cruz, $30 million for Billy Butler, $21 million for Michael Cuddyer, who played in 49 games last season. And $10.5 million for Torii Hunter, whom Detroit didn’t even want to retain. 

This is the winter to be a right-handed hitter on the free-agent market, because teams are flush with cash and many of them are trying to balance out lineups that have become too left-handed. For reference, here are the 30-year trends in the distribution of plate appearances between righties, lefties, and switch-hitting position players. 

The changes are fairly subtle, but note the distinct uptick in the red line, representing the share of plate appearances that have been given to left-handed batters over the years. While the number has historically been around 30%, it jumped up to 33% in 2008 and increased to 35% by 2014. Besides the one-year blip in 2002, the last seven years are the only seasons in the entire sample where left-handed hitters have been given one-third of all the plate appearances in Major League Baseball. 

The share of right-handed batters hasn’t varied much over the years, though it is a bit lower now than it was during the last decade, but not dramatically so. The real decline that seemingly has led to an increase in reliance on left-handed hitting is the decline in switch-hitting. Back in 1994, 20% of all plate appearances went to switch-hitters, but that total was just 14% last year, continuing a long-term trend away from allocating at-bats to guys who hit from both sides of the plate.

This decline in switch-hitting is fascinating, but is probably a subject for another post, as the reasons behind it are interesting enough to justify a few thousand words. For now, we’ll just note that the lack of switch-hitters available to balance out a lineup was initially offset by a rise in at-bats given to right-handed batters, but over the last seven years, righties have been slowly getting replaced by lefties, to the point where teams are now feeling quite vulnerable against good southpaws. 

The reasons for the decrease in right-handed hitting are still a subject of debate. As Joe Lemire argued on Grantland over the summer, it could very well be the result of a multitude of factors, including ballpark construction, a greater emphasis being placed on defensive value, and an expanding strike zone, in addition to the simple fact that pitchers are just throwing harder now than ever before. 

However, left-handed hitters are also facing an expanded strike zone, also are facing hard-throwing pitchers, and also have been squeezed out in favor of better defenders who might have been pegged as bench guys a decade ago, so these explanations don’t isolate why right-handers have been disproportionately hurt by the changes. And perhaps that’s because they haven’t been. Over this same time period, here is the trend in Isolated Slugging (Slugging Percentage minus Batting Average, which serves to remove the impact of singles from the calculation) for righties, lefties, and switch-hitters. 

Before the so-called "Steroid Era," there was no real difference in power output between right-handed and left-handed batters. But in 1997, left-handers began to see a surge in ISO that right-handed batters did not receive, and this advantage held mostly in place until 2011, when the equilibrium returned. From 2011-2013, both sides posted nearly identical ISOs, but then, in 2014, left-handed power collapsed to its lowest level since 1992, leaving right-handed hitters as the significantly more powerful group for the first time in 20 years. 

For all the hype about the lack of right-handed power in the game, it’s left-handed power that should have been put on a milk carton last summer. In the 2014 season, 38 right-handed batters hit 20 or more home runs, which was down a bit from the 40-60 range that the "Steroid Era" had made common, but still a reasonably decent number. You know how many left-handed hitters whacked 20 home runs last year? Only 15, down from 27 the year before, well below the 30-40 range established during the time when Barry Bonds reigned supreme. 

And it’s not just the lack of dingers; left-handed batters were far less effective in 2014 than they have been historically. To measure total offensive production relative to the average for each year, we can use wRC+, which baselines all performances to 100 for that given year. Here is the league average wRC+ for righties, lefties, and switch-hitters since 1984. 

For the last three decades, left-handed batters have been the predominant source of offense in Major League Baseball, well outpacing their right-handed brethren in production. Over the last four years, however, offense from left-handed batters has cratered, and right-handed production actually crept up high enough last year to pass lefties for the first time in the timeframe we’re looking at. It wasn’t just the home runs; righties were better overall hitters than left-handers last year, which is a stark reversal from historical norms. 

However, we have to keep in mind the trend that we showed in the first chart, because the production numbers we’re looking at here are likely the result of the shift in plate appearance allocations. As teams have shifted at-bats away from right-handers and switch-hitters to left-handed bats, they’ve been digging ever deeper into an already shallow talent pool, so the new inferior left-handed hitters who are getting playing time are dragging down the overall group’s average. Meanwhile, the good right-handed batters now make up a larger portion of their demographic, so their performances weigh more heavily in the group average. 

What we’re seeing isn’t necessarily decline from good left-handed bats or improvement from good right-handed bats; it’s a population shift of the inferior hitters from righties to lefties. Or, maybe more specifically, a shift from switch-hitters to right-handers, and then a shift from right-handers to left-handers, a total evolution that has taken place over the last 20 years. With more of the lesser hitters in the league batting from the left side, teams are finding themselves more vulnerable to left-handed pitching, and appear to be putting a higher value on the right-handed sluggers who can help provide offense against southpaws. 

So it appears that the idea of right-handed power going missing from the league might not actually be true. Instead, it appears that right-handed hitters as a whole have become more scarce, and thus teams are valuing right-handed hitters more highly in an effort to balance out their lineups. But why have right-handed hitters become more of a rare commodity? 

I can only speculate here, but perhaps it’s because we’re teaching natural right-handers to hit left-handed at an early age. According to Baseball Reference, there were 85 players in MLB last year who batted from the left side but threw with their right hand. These are natural right-handers who learned how to hit left-handed, but because it is more difficult and less useful to throw left-handed if you’re not a pitcher, they continue to throw with their dominant hand. 

If they had been left alone as children, they’d likely be right-handed batters today. And the proportion of this kind of player has grown dramatically in the last three decades. Here is one final chart, detailing the growth of players who hit lefty but throw righty and have been given at least 100 plate appearances in a season since 1984. 

These players have always existed, but there is no doubt that there are more of them now than there have been historically, and there are some pretty great hitters included in this group. Joey Votto, Robinson Cano, Prince Fielder, Chris Davis, Freddie Freeman and Bryce Harper are among the current players in MLB who bat left-handed but throw right-handed. Move enough of these guys to the other side of the ledger, and maybe we don’t have this run on right-handed bats that we’re seeing at the moment. 

Like all things in baseball, this is almost certainly cyclical, and the teams will force a move back to a right/left split that is more in line with historical norms. With the rise in shifts predominantly affecting left-handed hitters, it seems unlikely that it’s rational for teams to be giving as many at-bats to lefties as they are now, and I would expect to see an influx of right-handed hitters into line-ups over the next few years. The lack of run scoring in the game right now will cause teams to look for offensive advantages, and getting back to a more traditional number of left-handed hitters might be one way for teams to find some of the game’s missing offense.