Platoon Advantage: Hitters that Should See Better Results Against Left-Handed Pitching

With so many new and predictive statistics available to people that follow baseball, we sometimes forget to look at some of our old staples. Often times, this is with good reason. Things like xwOBA, batted ball data and wRC+ are more predictive than counting stats of yesteryear.

But one old school stat that we shouldn’t overlook is platoon splits. If a player is performing significantly different than their career norm against pitching of a certain handedness, this could suggest a regression (either positively or negatively) is coming.

Platoon splits are not an exact science. Just because a player has posted a wRC+ of 140 against left-handed pitching doesn’t necessarily mean their true talent level is 40 percent better than league average. And as many have noted in far more thoughtful and extensive work, they also take more time to normalize than we typically think. It’s possible that the trends I’m observing aren’t quite as relevant as they appear. However, the hitters listed below have significantly under performed their career norms to one degree or another and could see a bump in their production if it does revert to their typical level of performance.

Mookie Betts

No one expected Betts to repeat his MVP 2018 season, and his .261/.381/.456 slash line combined with 13 home runs and nine stolen bases is hardly killing you, but Betts looks to be in line for a big second half if he can hit left-handed pitching like he has in the past. Betts’ plate discipline and batted ball data all looks consistent with last season’s, the difference is he is slashing just .213/.323/.300 (57 wRC+) against left-handers – despite a career OPS of .936 (146 wRC+) against them.

Buster Posey

Posey is another veteran with a long track record of elite performance against lefties. Posey has a career .919 OPS versus left-handers compared to .797 against right-handers. This season his OPS is just .501 against lefties in 65 plate appearances. Injuries and age-related decline may limit the now 32-year-old’s ability to bounce back – he’s striking out more and walking less than he ever has before. Given Posey is still eligible at fantasy baseball’s biggest tire fire of a position, he could still be worth a flyer. It’s no guarantee, but there may be better days ahead, even if they don’t look like vintage Buster Posey.

Justin Smoak

Smoak, who was recently activated off of the injured list is an interesting case. In 2017-18, Smoak  hit left-handers well (121 wRC+), although the switch hitter had been far less productive against them (93 wRC+) previously in his career. So while Smoak’s track record is less extensive, there are reasons to think he can still rebound. According to Baseball Savant, he has one of the highest negative differentials between his wOBA (.263) and xwOBA (.328) versus lefties in all of baseball. The same is true of his batting average (.187) compared to expected batting average (.250). His strikeout and walk rates are also in line with his breakout 2017. With plenty of DH/first base types on the Jays’ roster, Smoak will need to battle for playing time, but there is a good chance he does rebound if given it.

Adalberto Mondesi

As I wrote last month, I think Mondesi may be a player who’s combination of poor plate discipline and average batted ball skills may be catching up to him. If I am wrong, it could be because he hits left-handers like he did in 2017-18. Mondesi is by far the youngest player on the list and less of a finished product than the others. He’s only had 260 career plate appearances against left-handers, so there’s less to be made of his struggles this season (76 wRC+) or successes previously (109 wRC+). I’d file Mondesi more under “worth keeping an eye on” more than I would “likely to rebound”.

Two Other Interesting Names: Vlad Jr. and Eloy

Baseball’s two highest regarded hitting prospects heading into the 2019 season have also struggled somewhat against left-handers so far in their rookie seasons – both posting an OPS under.730 and wRC+ under 100.

Eloy Jimenez and Vladimir Guerrero Jr., both right-handed hitters, hit left-handers well in the minor leagues. Expect improved performances against lefties to pull up their numbers in the second half of 2019 even if they continue to be challenged during their rookie seasons.