Adrian Gonzalez’s Evolution, Part I

This is the first of a two-part series on Adrian Gonzalez’s evolution as a hitter.

Writing for ESPN.com last year, Dave Cameron suggested that then-newly-acquired slugger Adrian Gonzalez was displaying a new approach at the plate in Boston. Cameron pointed out that, as of May 14, Gonzalez had significantly reduced his walk percentage (BB%) and increased contact on pitches outside the strike zone (O-Contact %). Like 2010, Gonzalez was back to swinging at more pitches, but was making contact on roughly 85% of his swings. That was a huge jump from his carreer average at the time.

Since we’re on the cusp of a new season, I thought it’d be interesting to revisit Gonzalez’s 2011 to see if those early season trends held for the entire year. Overall, Gonzalez put up a .406 wOBA in 2011, versus a .378 with the Padres in 2010. The smooth-swinging first basemen got on base more often and also slugged for a higher percentage —though his ISO numbers were nearly identical. So the question is this: Was his 2011 success due to a different approach?

To figure that out, I created a series of heat maps based on Pitch F/X data that compare Gonzalez’s performances in 2011 and 2010. For the first part of this series, I’m only focusing on his overall performance. In the second part, I’ll take a deeper look and mine his home-road splits.

The first thing we need to check on is whether opposing pitchers took a different approach with Gonzalez after his move to Boston. As the data suggest, pitchers didn’t appear to approach Gonzalez all that differently:

There are some small changes in certain zones, but pitchers were pretty consistent with Gonzalez. Even if you break out fastballs from off-speed pitches, the percentages are basically the same by zone between 2010 and 2011.

Despite the season-to-season similarities, though, we see striking differences in the slugger’s approach in different zones.

Gonzalez didn’t swing at more pitches in 2011, but he did alter what pitches he went after. The graphic below shows the difference between Gonzalez’s swing percentage from 2010 to 2011 in various zones:

We see that Gonzalez offered at more pitches on the outside of the plate, as well as down and in, and overall appeared to expand his zone in 2011. This is consistent with what Cameron observed last year. In addition to expanding his zone, Gonzalez increased his contact rate (Contact %) considerably from 78.7% in 2010 to a career-high 81.8% in 2011. The graphic below shows the difference in Gonzalez’s whiffs-per-swing in each zone between 2011 and 2010:

Looking at pitches on the outside of the plate — as well as pitches up in the zone — Gonzalez dramatically reduced his strikeouts. But did his change in swings translate to his performance?

The graphic below shows the difference in Gonzalez’s wOBA per swing in 2011, versus 2010, for different zones:

It seems we have our answer: Gonzalez raised his overall production relative to 2010 (153 vs. 143 wRC+), but here we can see exactly how he increased his production. Despite hitting the same percentage of batted balls the opposite way (28% in 2011 versus 28% from 2008 to 2010), Gonzalez increased his wOBA/swing by .087 on pitches up and away. He also  jumped roughly .035 on belt-high and low pitches on the outer half of the plate; he went up .097 on balls that were up high or in the middle of the plate; he increased his wOBA/swing by .062 on pitches belt-high and inside; and he saw a .049 jump on pitches down and in.

What’s interesting here is that Gonzalez increased his wOBA/swing on belt-high, inside fastballs by .062; but he actually decreased the number of pitches he swung at in this zone. If Gonzalez became more aggressive on outside pitches then that might have allowed him to be even pickier on pitches that were inside. And pitches that he may have avoided earlier because he was less productive on contact suddenly became much more productive, which freed Gonzalez to take a hack, rather than risking a called strike.

So what have we learned? At a high level, the data suggest that while pitchers didn’t appear to have altered their approach with Gonzalez, he still evolved at the plate. Gonzalez seems to have expanded his zone on the outside and around the letters — and he dramatically reduced the number of pitches on which he whiffed. What we don’t yet know is whether his performance change is attributed to the dimensions of Fenway Park, relative to Petco. Was Gonzalez emboldened, as Cameron suggested, by Fenway’s hitter-friendly confines — especially the Green Monster? To untangle this, we need to compare the difference in Gonzalez’s performance using home and road splits. If Cameron was right, we should see that Gonzalez’s appetite for balls on the outer half of the plate in 2011 was more prominent at home than on the road, especially when compared to 2010.

I’ll take a look at that in the series’ second part.




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Bill works as a consultant by day. In his free time, he writes for The Hardball Times, speaks about baseball research and analytics, consults for a Major League Baseball team and appears on MLB Network's Clubhouse Confidential. Along with Jeff Zimmerman, he won the 2013 SABR Analytics Research Award for Contemporary Analysis. Follow him on Tumblr or Twitter @BillPetti.


21 Responses to “Adrian Gonzalez’s Evolution, Part I”

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  1. Rufio Magillicutty says:

    That’s all fine and good, but these numbers outside the context of standard degrees of randomness for any player betray little significance, though conveniently an enormous facility for explanation.

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  2. mcbrown says:

    This is tantalizing analysis. However we don’t know (from the data presented here) how much of the increase in wOBA/swing we should attribute to BABIP “luck”, vs. BABIP “skill”. [I am assuming that none of the wOBA/swing change is attributable to a meaningful change in “power” in any zone, as his overall ISO didn’t change, and therefore an increase in ISO in any zone would show up as a decrease in another, but overall only two zones showed a decrease in wOBA and neither was significant.]

    I think we may need to see another half season or more of Gonzalez in Fenway to decide if he is able to take advantage of the park’s dimensions to sustainably improve his BABIP – it is certainly within the realm of possibility, if not probability.

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  3. Hurtlockertwo says:

    Big money, more pressure to perform. A.G. is a great team player and is willing to do anything it takes for his team to win.

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  4. Nice work Bill. One question: do you have these data broken down by road/home? In watching him last year he seemed to really enjoy taking those up/away outside pitches and peppering them off the green monster. Things that would have been lazy flyballs in Petco were often doubles in Fenway.

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  5. Slartibartfast says:

    All we really know is that a .380 babip is utterly unsustainable, and if he doesn’t start hitting for power and walking more his value is going to fall well short of what everyone expects.

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    • mcbrown says:

      Mr. Boggs’ 4 year peak (.378 BABIP) would beg to differ. His 7 year peak (.368) has some choice words as well.

      [And no, I’m not saying AG is the next Boggs. I expect his BABIP to decline. But at this point we cannot yet rule out the possibility that he is a hitter who can turn Fenway to his advantage and sustain a much higher than “normal” BABIP. There is enough anecdotal support of AG’s particular skills that I give this possibility more likelihood than if it were, say, Jason Varitek who posted a 0.380 BABIP last season. Another full season should let us know one way or the other.]

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  6. Mr Punch says:

    I’m a Sox fan concerned about AG’s long-term abilities, although if he hits enough doubles off the wall his BABIP may be more sustainable that it looks. Meanwhile, this is a very intelligent hitter who’s unusually articulate about it; I have to suspect that his presence contributed to outstanding years from two fellow lefties, Ortiz and Ellsbury.

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  7. jim says:

    ok, but how did his OPSBIs change?

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  8. North Sider says:

    Looks like Adrian Gonzalez adjusted his plate approach to Fenway. Impossible to hit bombs over the garage door, easy to flick the bat and get wall-ball doubles. I would say he has the sweetest swing of any batter currently lacing them up.

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  9. Shane says:

    The Walk rate is quite easy to understand. He was swinging at more pitches and being more aggresive due to hitting behind Ellsbury and Pedroia who were on base many, many times when he came to the plate. This would explain him swinging at more pitches outside the zone. Secondly due to better hitters hitting behind him he got pitched around less. In San Diego he batted in the middle of nowhere land. In Boston he was raking in the middle of the best top 5 slots in the majors.

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    • Amish_Willy says:

      Or perhaps he was swinging at more pitches with the Red Sox due to the increased liklihood of them falling for hits. For instance, at Petco those down and in pitches are just asking for a routine flyball to right-center where the ball goes to die. With his new home he had much more incentive to hack at those pitches versus waiting for something he could drive to left.

      I love it how a guy can hit .338 and fans will come out voicing concerns on his long-term ability. Blind to the rose on the nose.

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  10. Madoff Withurmoni says:

    I thought I read somewhere that he was forced to change his approach due to a bum shoulder. Wasn’t able to drive the ball out of the park as often.

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  11. pft says:

    At the end of the 1st half Adrian admitted that Fenway played a big part of his improved performance. How could it not given the high percentage of balls he sends the other way.
    \
    That said, Adrian wa not quite the same hitter in the 2nd half. Most of his improved performance came in the first half. He had a relatively poor 2nd half which same say is due to problems with his shoulder after the HR Derby.

    It would be interesting to see if there was any change in approach in the 2nd half as AL pitchers adjusted to Adran.

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    • Amish_Willy says:

      We always assume a drive off an outfield wall is a sure thing double, but for a wall as close as the green monster and a runner as slow as Gonzalez, is that the case?

      I ask because not surprisingly he hit more homeruns away then at home (17 to 10), but also more doubles (26 vs 19). He was really damn slow when he was 25, can only imagine what he’ll be like when he’s 35.

      His Home/Road ISO splits in 2011 are interesting:
      Home – .169
      Road – . 250

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      • pft says:

        A-gon is definitely slow, but on FB off the wall he is fast enough to get a double. LD off the wall are a different story.

        12 of his doubles and 7 HR came at home in the 1st half, only 7 doubles and 3 HR at home after the ASB ( I counted from the game logs so hopefully I counted right).

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  12. MGL says:

    “Overall, Gonzalez put up a .406 wOBA in 2011, versus a .378 with the Padres in 2010.”

    Don’t we need to park adjust those numbers before we speculate on why he has hit better in 2011? Maybe he has not hit much better after all.

    The wOBA PF for Petco is .92. So to park adjust his .378 wOBA, we can take a shortcut and divide by .96. .378/.964 is .394. That is his park adjusted wOBA in 2010.

    The wOBA PF for Fenway is 1.03. .406/.1015 is .400. That is his park adjusted wOBA in 2011.

    So now, the difference is only 6 points in wOBA, not a whole lot to get excited about.

    We should be using PF’s for LHB though. Let’s see.

    Actually, the PF’s for LHB in both of those parks are slightly reduced. So, instead of .92 and 1.03, we have .93 and 1.02. That would make their park adjusted wOBAs for 2010 and 2011 .392 and .402, a 10 point difference, still less than the non-park adjusted 28 points.

    I have little doubt that he has adjusted his swing more than the average LHB in Fenway, or that his natural swing is suited for that park. Surely a LHB who goes the other way is going to benefit from Fenway more than the average LHB.

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    • Bill Petti says:

      I’ll be looking at Park Factors in Part II. I think they might explain some of the production, but not the overall change in approach, obviously. Also, I think it’s more than just the change in home environment in terms of his outcomes.

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  13. KerryHofmeister says:

    He did mention on the ESPN Fantasy Focus podcast that he did have to change his approach due to a torn labrum in his non- throwing shoulder. I believe he said that he couldn’t finish in the same way he wanted too. I don’t know how it will change the data, but he did get it repaired in the off season.

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