Adam Dunn’s Changed Plate Approach

Suffice it to say that Adam Dunn‘s power has been eerily consistent throughout his career, hitting 40 +/- 2 home runs the past six years with over 100 RBI in five of them. His OBP, walk rate, and strikeout rate were very similar from 2004 to 2009. However, Dunn showed a change in approach last season, reaching career worsts in walk rate (11.9%) and strikeout rate (35.7%) while his OBP was his lowest since 2003 (.356). Granted, that’s still a very good OBP, but his change in approach came with an OBP drop of 40 points since he first joined the Washington Nationals.

Dunn’s swing rate has increased from 40.4% to 45.0%, a career high, showing a more aggressive approach at the plate. Here’s how his other plate-discipline stats changed:

2009: 19.4% O-Swing%, 65.5% Z-Swing%, 73.0% Contact%, 10.7% SwStr%
2010: 28.5% O-Swing%, 68.3% Z-Swing%, 68.2% Contact%, 13.8% SwStr%

As a consequence of his increased swing rate, Dunn whiffed on more pitches in 2010 mainly due to a 9% increase in swing rate on pitches outside the zone. The drop in contact rate shows that while Dunn swung more, he didn’t make more contact per swing. Swinging on more pitches did allow Dunn to make slightly more contact on a per-pitch basis, as he made contact on 30.7% of 2010 pitches vs. 29.5% of 2009 pitches. It’s also notable that the increased swing rate caused Dunn to see a career low 4.11 pitches per plate appearance compared to 4.32 pitches/PA in 2009. However, the fact to the matter is that Dunn’s OBP, walk rate, and strikeout rate were not favorable changes last season, which are all related results of plate discipline.

To investigate a bit more into Dunn’s changed plate approach, let’s look at how Dunn changed his swing behavior against different pitch types. The following graphs from the batter’s point of view are Dunn’s “50% swing zones” against fastballs in 2009 and 2010, a term coined by Jeremy Greenhouse:

What the swing zones tell you is a quick glimpse of Dunn’s swing rate by pitch location. If a fastball was located within the area, then Dunn is estimated to have swung at the pitch at least 50% of the time. If outside the area, less than 50% of the time. Comparing and contrasting swing zones are a simple way to show how a batter has changed his swinging behavior. It seems that the left-handed Dunn swung at more low fastballs from right-handed pitchers, a more aggressive approach, while swinging at fewer inside fastballs from left-handed pitchers.

Here’s a look at Dunn’s swing zones against breaking balls, not including off-speed pitches such as changeups:

The left graph shows a more aggressive approach against RHP sliders and curve balls in 2010, while the graph against LHP breaking balls show that Dunn started to swing more at outside and high breaking balls more often than low ones.

Let’s see how Dunn’s approach changed by the numbers based on these splits. Here’s a table of Dunn’s plate discipline statistics in 2009 vs. 2010 split by pitcher handedness and pitch type:

Swing% O-Swing% Z-Swing% Contact% SwStr%
2009 RHP FB 40.7% 18.7% 63.9% 80.3% 8.0%
2010 RHP FB 43.5% 23.9% 66.5% 73.8% 11.4%
2009 LHP FB 43.9% 21.6% 63.0% 72.8% 11.9%
2010 LHP FB 46.3% 29.0% 64.5% 67.3% 15.1%
2009 RHP SL/CU 33.7% 15.8% 56.5% 62.8% 12.5%
2010 RHP SL/CU 37.1% 24.0% 56.2% 53.9% 17.1%
2009 LHP SL/CU 40.2% 24.6% 58.5% 65.0% 14.1%
2010 LHP SL/CU 41.1% 31.0% 60.2% 63.6% 14.9%

Across the board, Dunn whiffed more often in 2010 because he swung at many more pitches out of the zone. In particular, RHP breaking balls caused Dunn to swing much more often out of the zone while his swing behavior in the zone was almost exactly the same. Contact percentage (per swing) did not justify the change in swing behavior and instead caused Dunn to whiff more and presumably walk less.

One last table for you. Dunn had a slow start in 2010 and while looking at his slash stats by month, I was wondering whether his swing rate by month said anything about his OBP. Here’s a look at how Dunn’s swing rate changed by month in 2009 and 2010 along with his slash stats:

April 2009 34.9% .310/.467/.606 | April 2010 40.2% .225/.361/.463
May 2009 39.2% .243/.349/.551 | May 2010 44.6% .313/.395/.616
June 2009 38.2% .241/.389/.437 | June 2010 47.2% .275/.330/.559
July 2009 39.7% .319/.427/.615 | July 2010 45.2% .284/.379/.580
August 2009 38.4% .297/.453/.659 | August 2010 43.9% .228/.342/.545
Sep/Oct 2009 45.5% .212/.322/.333 | Sep/Oct 2010 40.3% .227/.333/.432

There actually does seem to be some correlation between Dunn’s swing rate and his on-base percentage by month. Small sample aside, it’s clear that Dunn’s swing rate has increased across the board from 2009 to 2010. Whether that ultimately had an effect on his decreased walk rate and OBP, I believe the evidence says that Dunn’s changed plate approach did not benefit him in 2010.

Of course, this ignores the fact that Dunn is now with the Chicago White Sox, playing in a ballpark that’s much more favorable to left-handed hitting power hitters than when he was with the Nationals. But AL Central pitchers have heard of Dunn’s power, and if they decide to pitch around him (while noting that Paul Konerko will return to the lineup in 2011), Dunn’s pitch recognition will be tested, especially if he continues to be aggressive while swinging at pitches out of the zone. Unsurprisingly, Dunn projects to hit 40 home runs again by most projection systems, but opposing pitchers will use every bit of information they can get to mitigate the damage if they realize that Dunn has indeed changed his plate approach.

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Albert Lyu (@thinkbluecrew, LinkedIn) is a graduate student at the Georgia Institute of Technology, but will always root for his beloved Northwestern Wildcats. Feel free to email him with any comments or suggestions.

16 Responses to “Adam Dunn’s Changed Plate Approach”

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  1. Telo says:

    Very interesting. Living in DC last year, the local media would talk about Dunn’s change of approach quite a bit, and it’s awesome to see exactly how he expanded his zone.

    And while you showed pretty clearly that he swung more, chased more, whiffed more, and walked less… that stuff was all pretty obvious. Anyone watching him could tell you that. I was kind of hoping for an answer as to whether or not this drastic change was beneficial or not. His wOBA was a few pips lower than his career mark, but I bet with some real analysis you could take a good guess as to whether or not this is a good move in the long term.

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    • Ryan S says:

      How is chasing more, whiffing more and walking less EVER any good? Unless increased swing rate = increase in SOMETHING then no, it’s not a good move. This would ONLY ever be good if all pitchers never changed their approach.

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  2. Matty Brown says:

    maybe he was just anxious to get out of Washington.

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  3. Dan says:

    I remember hearing, from most likely an untrust-worthy source, that he was pressured to be more aggressive in Washigton. Can anyone confirm this, or has anyone else heard the same?

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    • Rizzo I aint says:

      Dan, that’s true. The change came from hitting coach Rick Eckstein and Dunn himself.

      They both agreed he wasn’t aggressive enough… and for whatever reason they thought it better to exchange lower OBP for a higher AVG.

      I kid you not, that was the strategy.

      Sure, he hit for a higher average… but he took less walks as a result and his overall OBP fell because of it.

      I expect you’ll see ‘vintage’ Dunn from here on out now that he’s out of DC. Especially if he works with a hitting coach that lets him know its ok to walk.

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      • Colin says:

        One of Dunn’s stated goals for last season was to hit .300. He didn’t. In fact his average fell from .267 to .260. At least part of his decline in OBP was due to his drop in average (in addition to a lower walk rate.)

        However, it shouldn’t be viewed as decreasing OBP for AVG, but as decreasing OBP for SLG. Dunn clearly isn’t a slap single hitter. His average hit is worth quite a bit more than the marginal additional value of a single over a walk. He had 76 extra base hits (35 2b, 2 3b, 38 HR), which was more than his previous 5 seasons (though below his 2004 & 2005 seasons). This lead to a slight uptick in SLG over 2009 (and 2008).

        Even with his changed approach, it was still one of his better years. It was his 3rd best WPA season (after 2004 & 2005), and 2nd best WAR (the shift to 1st helped).

        Regardless of whether this was the best approach, it clearly wasn’t a bad approach. When he can combine his power with patience and not passivity, he’ll have another monster year like 2005.

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  4. Brad Johnson says:

    A look at a similar lefty, Ryan Howard, will reveal not only an expanded strike zone but also an increase in contact rate. Feel free to run with that.

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  5. Bob says:

    Batter hits as part of a lineup and Dunn in Washington was expected to be the big bopper from the cleanup spot, not just a HR machine with a high OBP. Though a fan favorite, and one who repeatedly lobbied for a contract extension in D.C., Dunn could be maddingly frustrating with his low contact performance and subpar defense if forced to play in the field. Nats fans wish him well in Chicago but hope that the Chisox faithful don’t turn on him if he’s not all that you’ve cracked him up to be.

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  6. Pg says:

    It’s already been well documented the change in approach was sparked by the nats hitting coach.

    I don’t like Greg walker, but he works well with sluggers. I’m not worried at all about Dunn.

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  7. kick me in the GO NATS says:

    I think it is obvious, but being in a bad lineup hurts good hitters a lot!

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  8. adohaj says:

    I hope Rick Anderson reads this….

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  9. dickysty says:

    It was a contract year. Hit home runs get paid more, simple.

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  10. Very bad instruction for Mr. Dunn. He needs to sit down with a laptop and me for a light lunch. I can absolutely help him increase contact rate – which, with his power, will jump his homer totals up to 60, easy. look me up. try mortimerzilch
    on g mail. or visit my website to make contact. You and Kevin McReynolds are my dream targets, but Big Mc hasn’t answered me either, yet. Do so why don’t you?

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