wRC+ and Handedness: The Importance of Being Lefty

I think we’re all aware that the lefty vs. righty matchup favors the batter.  But to what extent?  And what are the implications?  Prepare to be inundated with a bunch of charts and tables.

For the purposes of this article, I’ll be sticking to using wRC+, my favorite all-in-one, level-playing-field batting stat.  My sample consists of all batters from 2002-2012 who had at least 200 total PAs against lefties and at least 200 more against righties.

The charts in this article will break down the frequency distributions of wRC+ for left-, right-, and switch-hitting batters, grouped to the nearest multiple of 10.  For example, the chart below shows that 21.5% of right-handed batters (RHB) hit for over 85 but less than or equal to 95 wRC+ against right-handed pitchers (RHP).

(Mouse over or tap image to see splits against LHP, Left-Handed Pitchers):


“BHB” is what I’m calling switch hitters (Both-Handed Batters).  In my sample, by the way, there are 193 LHB, 386 RHB, and 104 BHB.

      Average wRC+  PA-Weighted Averages
 RHP  LHP Overall  RHP  LHP Overall
LHB 110.0 84.9 103.8 114.0 91.3 108.1
RHB 88.8 107.5 94.8 96.3 112.2 100.8
BHB 94.0 90.4 93.3 100.7 98.1 100.0

Now, looking at the overall numbers, you might be tempted to say that being a left-handed hitter is a pretty big advantage.  Well, considering over 72% of all batters’ PAs are against right-handed pitchers, that would make some sense.  But then again, switch hitters hit lefty too… maybe it’s just that lefty batters of late were simply better hitters.  And, who knows — maybe switch hitters generally lack the experience hitting as a lefty that true lefties have… or maybe, a lot of the time, it was being a more marginal talent in the first place that led them to learn switch hitting.

% of PA vs. RHP % of PA vs. LHP
LHB 74.2% 25.8%
RHB 71.4% 28.6%
BHB 72.0% 28.0%

Instead of looking at how whole groups of batters fare overall, let’s look at the differences within individual batters.  In the next graph, you’ll see the distribution breakdowns of hitters’ wRC+ against righty pitchers subtracted by their wRC+ against lefties.  Sorry, no mouse-over surprise for this one:


For the following table, the PA-weighted averages go by whichever PA count is smaller — vs. RHP or vs. LHP (which pretty much is always vs. LHP).

wRC+ Against RHP Minus wRC+ Against LHP

Average Standard Deviation PA-Weighted Average
LHB 25.2 21.3 25.7
RHB -18.7 20.8 -17.7
BHB 3.6 23.2 2.8

It’s probably a little more apparent in the table than the graph, but I’d say recent lefty batters legitimately have shown themselves to be more affected by the handedness of the pitcher, for whatever reasons.  If you refer back to the first table, you’ll see that, in particular, lefty batters suffer more against LHP than righties do against RHP.  To further explore that avenue (mouse over or tap for LHP, again):


                        Average wRC+ Differentials

RHP-Overall LHP-Overall
LHB 6.2 -18.8
RHB -5.9 12.6
BHB 0.7 -2.8

                                Standard Deviations

RHP-Overall LHP-Overall
LHB 5.5 16.4
RHB 7.4 14.0
BHB 6.5 16.8

What you’re seeing here of course has a ton to do with the aforementioned fact that hitters generally face righties more than 70% of the time, which skews their overall numbers in that direction.  But just keep these differences in mind as a rough adjustment to make to a batter’s wRC+


There are major, real differences between hitters in how well they handle opposite-handed pitching.  How consistent a player is in this regard, vs. how much you can expect them to regress to the mean, is a topic for another article.

For now, here’s a sortable list of the discrepancies between batters’ wRC+, in terms of RHP minus LHP (R-L) and in terms of Opposite minus Same-handed pitching (O-S).  You should be able to change the “200” you see as the minimum plate appearances to whatever you’d like, and it will filter the list (just re-sort after changing it).

Discuss Amongst Yourselves

So, it seems pretty clear that recent lefties have benefited a little bit more than righties when facing opposite-handed pitching, but suffered considerably more when facing same-handed pitching.  Since a lefty batter has plenty more opportunities to face opposite-handed pitching, the net result benefits them… but still, how can we explain why their fellow lefties give them such problems?  Is it relative lack of exposure to lefty pitching?  Could umpire strike zone differences have something to do with it?  Facing more specialist relievers?  Let me hear your thoughts, and maybe we’ll get a follow-up out of this…

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I’m hanging my hat on the exposure argument, primarily. LHB may get well into their MiLB career before they start facing a lot of LHP, so they get a late start on really developing the skill of handling pitches coming from the same side. But even if they never develop it well, the fact that they’re going to face 80% RHP in their career doesn’t retard their advancement.

It is the fact of the split that allows LOOGYs to exist, not the existence of LOOGYs that exacerbates the platoon disadvantage.

Umpire strike zones likely do have something to do with it, but I’d be surprised to see that the effect would explain the majority of the difference.

MHO, of course.


“Umpire strike zones likely do have something to do with it”

This. I’ve never understood why the outside strike to the left-handed batter is just a commonly-accepted “thing.” How did it come about, and why does it persist?

You know what I’d love to see, actually? A GIF comparison of some outside called strike threes against LHB vs. the nearest-to-identical mirror-image pitches against RHB. It might help us appreciate just how ridiculous those outside strikes are.


This image (from a couple of THT articles that is almost 6 years old now) is really all you need to see.


This image is actually probably the one you meant to link – it’s the revised version from the later article – and it’s corroborated by what we see called on a daily basis.

What I’m talking about, though, is actual in-game footage of those outside called strikes on lefties, compared to similar mirror-image pitches thrown to righties. I want to see what it actually looks like when a lefty takes a curveball two inches outside for strike three, and a righty takes a curveball two inches outside for ball four. I want to be told to imagine that pitch to the righty being a called strike, and I want to indignantly exclaim, “no!”

Dan Farnsworth
Dan Farnsworth

I think it has to do with a catcher’s glove side being much easier for him to receive quietly and without as much movement. Umpires usually set up in the lane between hitter and catcher, leading the outside pitch to both hitters to disappear for the last 6-12 inches of ball flight (at least). This forces them to go off of the catchers’ effort or lack thereof in getting to the ball as at least a small portion of their ball-strike judgment. That’s the best I’ve made sense of it anyway. I have studied a lot of the research out there and have done a lot on my own to help teach catchers in the baseball academy I work at.