A PitchFX Look at A-Rod’s Bizarre Reverse Platoon Split

This post originally appeared on Yankeeist.

It’s no secret that Alex Rodriguez produced the lowest full-season wOBA of his career in 2010 — his .363 mark was fueled by career-lows in batting average (.270), on-base percentage (.341) and the second-lowest full-season SLG of his career (.506). That these numbers were not only dramatically off from his superb 2009 (.286/.402/.532; .405 wOBA) but his majestic career triple slash (.303/.387/.571) suggests to me that he should be due for a reasonable bounceback. While it’s not impossible Alex has reached an irreversible decline, he’s been too historically good for me to be willing to write him off just yet. I won’t go so far as to proclaim that the Yankees are going to be getting .400-plus-wOBA A-Rod back, but as I’ve noted on at least one occasion this offseason, all A-Rod needs to do is exercise just a tad more patience and a wOBA in the .380s should be more than doable.

However, one curious aspect of A-Rod’s disappointing 2010 that I haven’t seen explored too in depth anywhere is the bizarre reverse platoon split/vanishing act he pulled against lefties. Granted, A-Rod is a bit of an odd duck in that he’s always hit same-handed pitching better than opposite-handed pitching, but this past season Alex wOBA’d a strong .380 against righties in 423 plate appearances, yet managed only a paltry .323 mark against southpaws in 172 PAs. In 2009 he wOBAed a robust .402 against lefties and .400 against righties, and during his career he’s punished lefties to the tune of a .395 wOBA (.413 against righties). So what caused Alex to lose .079 points of wOBA against lefties in 2010?

For the answer, we turn to Joe Lefkowitz’s wonderful pitchFX site, which I became aware of a couple of months ago but only recently started seriously playing around with, and have since found a seemingly limitless treasure trove of granular data. Here’s A-Rod’s 2010 player card. For 2009 you’ll have to select “2009” from the drop-down menu directly below his name, as there’s no direct link. I recommend right-clicking and keeping both pages open in separate tabs if you’re interested in taking a look at the data I’m about to reference.

Per the Pitch Outcome chart, Alex went from seeing a four-seam fastball in just over half of the pitches he saw against lefties in 2009 down to 35% four-seamers in 2010. He also swung at those four-seamers more often (41% in 2010 to 37% in 2009), hit 48% of the four-seamers he put in play in the air, and 1.9% of them went for a home run (in 2009 he lofted 38% of the four-seamers he put in play and 1.1% of them left the ballpark).

The decrease in four-seamers was countered by a dramatic increase in two-seamers (5.4% to 15.3% in 2010) and cutters (0.9% to 7.2%); the latter of which he pounded into the ground more than any other pitch he received from lefthanders (57.1% GB%) in 2010 and also swung and missed at more than any other pitch (39%) except the split-fingered fastball from righties (63%). He also compiled his second-lowest FB% against the cutter vs. lefties and hit none of the 54 he saw out of the park. Anecdotally, I recall thinking that Alex’s bat looked a tick or two slow against the fastball often throughout the first half of the season, and even wrote about it, and this information would appear to support that idea.

In any event, while the sample size is relatively small, I think we can safely say part of A-Rod’s troubles in 2010 were related to the cut fastball.

Alex also struggled mightily against the lefthanded changeup in 2010 (as did seemingly everyone else on his team), swinging at the 120 of them he saw 55% of the time, connecting with 70% of them and hitting them on the ground 54% of the time. He only lofted 31% of the lefthanded changeups he hit, and none of them cleared the seats. In comparison, in 2009 he swung at 46% of the lefthanded changeups he saw, connected with only 58% of them, but hit them in the air half the time and saw 1.1% leave the stadium.

These deficiencies against the lefthanded cut fastball and changeup are most glaringly apparent in the nine-quadrant heat charts (fastballs and off-speed pitches vs. righthanders and lefthanders) at the bottom of his player card pages.

Against 26 lefthanded fastballs thrown right down the middle, Alex only slugged .143. He basically got killed by lefthanded fastballs on the outer half of the plate, as well as down-middle and down-in. The only quadrant he handled himself with alacrity against lefthanded fastballs was middle in, where he crushed to the tune of 1.125 SLG against 49 pitches — the most he saw in any zone against lefties. All told, only two of the nine quadrants were red (or “hot”) for Alex; compared to five in 2009. He appeared to experience the biggest drop-offs on those down-middle and down and in pitches, going from slugging 2.143 and 1.333 respectively on 36 total pitches, to .250 and .333 SLG respectively on 40 total pitches.

His offspeed chart is also ugly — in 2009 he was “hot” in six of nine quadrants against lefthanded offspeed pitching, while in 2010 he was “hot” in only three, and one of those three was only lukewarm. Similar to lefthanded fastballs, he also saw a decline down-middle against offspeed, falling to a .400 SLG on 17 pitches from a 1.000 SLG on 20 pitches.

Alex was also blue down-middle against righthanded fastballs, and mildly blue down-middle against righthanded offspeed pitches this past season. However, in 2009, he was red hot in that same quadrant against lefties in both pitch categories, and red-mild against righties.

Before drawing any conclusions, it’s worth again noting that this analysis comes with an important caveat: given that there are far less lefthanded pitchers than righties in MLB, there is obviously less data to draw from, and so the sample sizes being discussed in this piece should probably be taken with several grains of salt. That’s not to say that they can’t be instructive or informative, but there probably isn’t enough data here to draw any seriously meaningful conclusions regarding A-Rod’s struggles against lefties in 2010.

That being said, Alex Rodriguez’s struggles against lefthanded pitching appear to have been due to a couple of factors: he had significant trouble in 2010 with the cutter and the changeup, the latter of which southpaws threw at him more than any other pitch (16%) except the four-seamer (35%). Alex exhibited a noticeable decline in his ability to turn on these pitches in specific quadrants of the hitting plane, leading to a greater success rate in many of the quadrants for the opposing pitcher and resulting in lefties throwing slightly more pitches into those blue zones.

Larry Koestler eats, drinks, sleeps and breathes the Yankees at his blog, Yankeeist. He previously contributed “What’s Behind A-Rod’s Power Outage: The Sequel” to FanGraphs’ Community Research blog.