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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41 Responses to “wRC+ and Handedness: The Importance of Being Lefty”

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  1. NatsFan73 says:

    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.

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    • Aaron says:

      “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.

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      • joser says:

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

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        • Aaron says:

          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!”

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      • Dan Farnsworth says:

        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.

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  2. Persona non grata says:

    On iPad and cannot mouse over. Separating out the LHP graphs would be much appreciated.

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  3. David Bruno says:

    Would be interesting to see the analysis decomposed between right-handed starters and right-handed relievers, and left-handed starters and left-handed relievers. Might help to analyze the effect of specialist relievers.

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  4. CSJ says:

    Something I noticed when looking at home run angles is that lefties are just better at hitting to the opposite field. It shows versus both RHP and LHP. I think these two concepts are related.

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  5. Neil says:

    The data set is large enough that this shouldn’t matter, but how much of an impact is Bonds having? He constitutes the top three observations and is quite a bit ahead of the rest of the pack, which would make those data points pretty influential. Worth considering at least.

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    • Removing Bonds subtracts half a point from the all the overall averages for LHB (1 point from the weighted ones) in the first table, so, you’re right, it’s a big deal. It’s more like 1.2 in the weighted of LHB vs. LHP, even, since Bonds had a lower R-L split than most lefties (11).

      So, really, the main thing that happens is lefty batters look even worse against lefty pitchers without him.

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  6. Youthful Enthusiast says:

    I’m with you on this one. I think Tango looked at this before and most seemed to agree that many hitters, especially HS ones, don’t see QUALITY LHP until they’re well into their professional careers. Quality RHP can be seen much earlier in a hitter’s career.

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    • Yeah, I don’t know if any studies have been done about what % of little league, high school, or minor league pitchers are lefties, but I imagine the lower down you go, the percentage gets much closer to the overall population’s percentage of lefties, which I believe is around 10%.

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      • jfree says:

        I’m not sure that’s true. As a lefty kid, you are excluded (via arbitrary decision of coaches) from playing most positions except P, 1B, and the 3 OF positions. So any lefty who wants to play baseball needs to play in one of those niche positions – or find a different sport. That is what drives the higher % of LHP (relative to population) early on.

        My guess at to the cause here re non-pitcher LHB is that same issue applied to career expectations. Statistically, you are looking at a different distribution of player positions and batter “types” when you look at “lefty” v “righty”. There is no such thing as a true lefty (ie bats and throws lefty) who plays any of the positions (esp 2B/SS/C) where a true righty can be a slap/contact hitter glove-first type of player. Assuming the lefty kid never goes down the pitching route – the positions generally open to him are 3 big power bat (1B, corner OF) positions or speedster CF. And power bat types are generally going to have higher “outcome” (wRC+ being an outcome) variance.

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        • jfree says:

          Just did a search on infield lefties (since LHB are generally going to be lefty throwers too)

          Half a GAME at 2B played by a lefty (Don Mattingly) in 1983

          Zero field appearances by a lefty at shortstop since 1905

          A few partial games by lefty catchers (last one in 1989) – but last lefty primary catcher was 1903.

          A few games by lefty 3B since 1905 (most recent 3 games by Don Mattingly in 1986)

          So yeah — LHB and RHB are a very different universe of player types

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        • jfree says:

          Further — looked at some of the “non-typical” LHB – eg Wade Boggs batted lefty – but he is a natural righty who learned how to bat left. Don’t know why/when he made that switch over but that too would indicate a different type of batter. More akin to switch-hitters.

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        • OK, good points. I’m sure you’re right that a lefty will be more likely to be pushed into being pitcher. But only about 1/4 of the roster spots are off-limits to lefties, which would mean that in a random sample, assuming the population is 10% lefty, you’d only expect about 13.33% of pitchers and all of the players other than 2B/SS/C/3B to be lefties. Assuming 12 pitchers on a staff, you’d also therefore expect lefties to make up 7% of position players overall.

          By the majors, nearly 30% of pitchers and over 40% of batters are effectively lefties (including switch-hitters)… clearly, a lot of “natural selection” is taking place along the way.

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        • jfree says:

          The “natural selection process” of lefties happens VERY early on – in Little League and in my experience is quite a bit different than you describe. There are four positions exclusively for righties (2B,SS,3B,C); one generally for lefties (1B), three “competitive”, and pitcher. Any utility or multi-position player is going to be righty – as is any backup catcher. On your typical Little League team (roster max of 15) with 2 lefties – one will be 1B/OF (younger), one will be P/1B (older). Most LL rosters don’t have more than 5 pitchers but that is still 20% LHP.

          The main “natural selection” occurs as kids grow into different body types. The big strong lefty can still play in LF/RF/1B but only has a handedness advantage at 1B. The big strong righty has C/3B/LF/RF – but 9x more big/strong players. The speedster lefty has CF – the speedster righty 2B/SS/CF with 9x the number of players. In all of those except 1B, the position player advantage will go to the righty if the bat is equal because of the positional flexibility. And every other body type who is lefty will gravitate to pitcher.

          LHB is a bit different because switching bat swing (big muscle control) can be learned far more easily than can switching throwing hand (small muscle control). As pitchers begin to throw breaking stuff, there is an advantage to righties who can make the switch to batting lefty – but little/no advantage for lefties to switch to batting righty. And the number of LHB begins to grow.

          That’s actually one reason for the bigger split difference IMO. RHB are virtually all “natural” righties. LHB are a mix of “natural” lefties (the two body types above) and “learned” LHB’s (all body/batter types). Both of those – a subset of body types (power expectations) and a more recently “learned” muscle behavior – would tend to produce bigger splits.

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        • evo34 says:

          jfree, what are you talking about? There are many more LHB infielders than you mention. Alex Cora, Ramon Vazquez, Stephen Drew are recent examples. Of course no one plays 3B through 2B as a left handed thrower. For the same reason there would be no left-handed QBs in the NFL if you were forced to roll out right on every play. Simple physics. Hardly an “arbitrary decision of coaches”.

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        • jfree says:

          There is a difference between a righty learning to bat left handed and a lefty batting left handed. Virtually all throw-righties bat-lefties are natural righties.

          Doing some stuff the other-handed way doesn’t make you other-handed. If you can’t understand this, you are almost certainly right-handed.

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  7. Brady says:

    I’m thinking facing a left handed reliever a night might have something to do with this. This all rides on how often they face LOOGYs though.

    Why do people go to the bullpen? Because they weren’t good at starting among things, but also the lack of developing a third pitch, which most of the time is a changeup. Fastball and breaking ball are usually already apart of the package. No matter how dirty your slider and fastball are, you probably won’t see the light of day in a rotation if you can’t throw that third pitch to get opposite handed hitters out. LOOGYs tend to have excellent breaking stuff that same handed hitters have a hard time hitting. I wonder if the PAs against are large enough and the results are bad enough for that to cause a discrepancy in results.

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    • Could be. How strict of a definition of LOOGY do you all prefer, if I were to look into this? 0% righties faced? 10%?

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      • Nathaniel Dawson says:

        A minimum percentage of appearances in relief, so you aren’t getting spot starter/long relief guys, and a minimum percent of lefties faced. Something maybe like maybe 90% for appearances, 80% for batters faced?

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  8. Sleight of Hand Pro says:

    im gonna go with the rotation of the earth theory. dont ask me to go into any more detail than that, cuz i wont.

    its the rotation of the earth.

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  9. philosofool says:

    Three hypotheses, with a little reasoning to justify them as plausible:
    (1) It’s an experience thing. LHP are rare so it’s harder to learn how to exploit the advantage for RHB or how to deal with it for LHB.
    (2) It’s a selection pressure issue. If you are a LHB who can only hit RBP, you can advance because that will be about 2/3 of your PA; if you’re a RBB who can only hit LHP, you can’t advance because that’s only 1/3 of your PA.
    (3) Premium defensive positions, except CF, require right handed throwing, or at least, that’s the perception of baseball coaches and managers everywhere. (Tango had a nice thread on this topic awhile ago and there was some sense that this “necessity” is really just one consideration among many.) If guys with “premium bats” simply have larger splits, usually, and being right handed is anti-correlated with a premium bat because of this defensive consideration, you would expect this result. Note that LHB are about 10% better than RHB overall. (I feel like there may be a hidden assumption here.)

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    • Yeah, I like #2 a lot.

      #3, I was able to test out a little bit. I got a 0.29 correlation between batters’ Opposite-Same wRC+ gaps and overall wRC+ for lefties, which would seem to support your idea that the better hitters have larger splits. However, for righties it was only 0.06. So, for some reason that principle apparently doesn’t apply to righties… odd, right?

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    • jfree says:

      #3 would lead to two things:
      1. “natural” (those who throw/write leftie since that is the small muscle control stuff) lefties do have to be power bat types or DH’s – because they aren’t allowed to play any other field position. Personally I do think that power batters probably do tend to have bigger splits.

      2. “natural” righties can learn to bat left far more easily than natural lefties can learn to throw right. Same with swinging a golf club or tennis racket and such. And there is an advantage to trying to do that because of the advantages of opposite-handedness re breaking pitches. The result though is that a larger portion of the LHB universe is “learned” LHB which may result in larger splits – ie #2 kicks in for them.

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  10. austin says:

    I think it’s a selection bias, in a way. Since 70% of pitchers are right handed, you need to be able to hit right-handed pitching in order to make it to the majors. In addition, most players are best against opposite handed pitchers. That means that Leftys who have a problem with same-sided pitching make it to the bigs at a much higher rate than rightys with the same problem, since most of their at bats will come against Right handed pitchers. The average righty batter has a smaller platoon slip because if he couldn’t handle right-handed pitching at least a little, he never would have been promote in the first place. Heck, some rightys even have reverse platoon splits, something I expect to be much more common in rightys than leftys.

    Again, it basiclly comes down to the fact that the one thing you have to be able to do to reach the bigs is hit Right-handed pitching.

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  11. Dave says:

    Thanks for the info. Sorry to sound like a novice, but where can I find the list of lefties who make up this list? (I’m quite new here) It would be of great help, as this is a tactic I decided to focus on when I was drafting.

    Many thanks.

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    • Unfortunately, I don’t think you can filter players by handedness at FanGraphs just yet — you can only do vs. lefty or vs. righty splits. If you’re handy with Excel, though, you can download the spreadsheet on this page (click the greenish icon at the bottom of the Excel Web App) and do a VLOOKUP to apply the handedness from there to whatever spreadsheet you download from the Leaderboards, based on player names (just watch out for players with the same name…).

      But the simpler way would probably be to just look up the platoon splits at Baseball Reference: http://www.baseball-reference.com/play-index/split_finder.cgi?type=b … which won’t give you wRC+ or wOBA, however.

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  12. Dave says:

    That’s great. Thank you. My Firefox blocker had blocked the link, so I can see it now.

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