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October 19, 2009

Ahead in the Count

Park-Adjusted Slugging

by Matt Swartz

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A few weeks ago, I introduced a new metric to evaluate team defense called Slugging on Balls in Play (SLGBIP), to be used in conjunction with Defensive Efficiency (DE) or Park-Adjusted Defensive Efficiency (PADE). The importance of this stat is that a simple consideration of how many outs a team makes does not entirely evaluate how well the team prevents runs. When we evaluate team offense, we consider team slugging more important than team batting average; if a team defense's only goal was to make outs, they would play their outfielders in and their corner infielders off the lines constantly. Since they do not, seeing how well they prevent extra-base hits is important as well.

However, many readers pointed out that certain parks are more conducive to preventing extra-base hits than others, and a metric such as Slugging on Balls in Play might have some inherent biases towards teams who play in stadiums where it is difficult to hit doubles and triples. Fortunately, there was already a method in place to adjust for this. In 2003, James Click introduced a new measure, PADE, in which he made park factors equal to the ratios of Defensive Efficiency at home versus on the road for the previous three years. I decided to reevaluate my analysis of 2007-2009 from my previous article by generating ratios of home and road Slugging on Balls in Play for 2007-2009. I did this for all teams except for the three that moved into new stadiums in the last three years: the Nationals, Yankees, and Mets. For the Yankees and Mets, I just used 2009 data to create their SLGBIP Park Factor for their current home fields, and 2006-2008 data to create their SLGBIP Park Factor for their previous home fields. For the Nationals, I used 2005-2007 to get their RFK Park Factor, and 2008-2009 to get their Nationals Park PF. Then I generated Park-Adjusted Slugging on Balls in Play (for yet another acronym, how about PASBP), which is transformed to represent the percentage difference in SLGBIP that their defense allowed relative to league average, and took the negative of this value so that positive numbers imply good defense. Here are the 2009 SLGBIP and PASBP rankings next to each other:


2009
Rank Team     SLGBIP  Rank Team       PASBP
  1  Mariners  .354     1  Mariners   7.293
  2  Dodgers   .360     2  Giants     7.156
  3  Reds      .371     3  Cubs       5.927
  4  Giants    .371     4  Dodgers    3.990
  5  Cubs      .372     5  Reds       3.352
  6  Rangers   .374     6  Rangers    3.318
  7  Cardinals .379     7  Tigers     1.334
  8  Yankees   .379     8  Rockies    0.724
  9  Padres    .380     9  Marlins    0.432
 10  Phillies  .381    10  Red Sox    0.425
 11  Rays      .383    11  Rays       0.276
 12  Tigers    .383    12  Phillies   0.130
 13  Twins     .386    13  Indians    0.130
 14  Angels    .391    14  White Sox -0.419
 15  White Sox .392    15  Cardinals -0.682
 16  Athletics .394    16  D'backs   -0.938
 17  Mets      .395    17  Royals    -1.185
 18  D'backs   .397    18  Twins     -1.150
 19  Rockies   .397    19  Angels    -1.680
 20  Brewers   .397    20  Yankees   -2.737
 21  Indians   .400    21  Padres    -4.081
 22  Marlins   .402    22  Orioles   -4.428
 23  Astros    .406    23  Blue Jays -4.997
 24  Pirates   .406    24  Braves    -5.739
 25  Red Sox   .406    25  Brewers   -5.791
 26  Braves    .406    26  Mets      -5.882
 27  Blue Jays .406    27  Athletics -7.120
 28  Royals    .406    28  Astros    -7.731
 29  Orioles   .410    29  Pirates   -9.193
 30  Nationals .418    30  Nationals -9.420

The most obvious example of a big change between the two rankings is the Red Sox, who went from 25th in SLGBIP to 10th in PASBP. That makes good sense, because the Green Monster is very conducive to doubles, and ignoring that makes it look like the Red Sox defense is especially vulnerable to surrendering doubles. The Padres went in the other direction, sitting at a respectable ninth in SLGBIP, but after adjusting for park, they fell to 21st. Their SLGBIP at home over the last three years is .357, but on the road it is .409; Petco Park is very difficult to hit extra-base hits in, as well as being difficult to hit home runs. Other notable changes included the Marlins, who went from 22nd to ninth after adjusting for park, the A's going from 16th down to 27th, and the Yankees falling from eighth to 20th, while the Royals went from 28th to 17th, and the Rockies saw an improvement from 19th to eighth after adjusting for the fact that they play in double-icious Coors Field.

How does this effect the evaluation of previous years? Let's look at 2008 and 2007:


2008
Rank Team     SLGBIP  Rank Team        PASBP
  1  Rays      .376     1  Red Sox     7.531
  2  Brewers   .378     2  Cubs        4.599
  3  Mets      .379     3  Marlins     4.310
  4  Blue Jays .380     4  Indians     3.564
  5  Padres    .382     5  Rays        2.873
  6  Red Sox   .382     6  Royals      2.521
  7  Athletics .384     7  Brewers     2.240
  8  Orioles   .386     8  Blue Jays   2.126
  9  Cubs      .386     9  Orioles     2.106
 10  Angels    .386    10  Angels      0.664
 11  Dodgers   .389    11  Mets        0.501
 12  Phillies  .390    12  Phillies    0.461
 13  Indians   .390    13  D'backs    -0.129
 14  Marlins   .391    14  Giants     -0.302
 15  Twins     .392    15  Dodgers    -1.014
 16  Astros    .394    16  Astros     -1.017
 17  Royals    .395    17  Athletics  -2.040
 18  Nationals .397    18  Twins      -2.161
 19  Yankees   .399    19  Padres     -2.824
 20  Cardinals .400    20  White Sox  -2.825
 21  D'backs   .401    21  Tigers     -3.653
 22  White Sox .403    22  Nationals  -3.682
 23  Tigers    .406    23  Cardinals  -3.733
 24  Giants    .407    24  Yankees    -3.764
 25  Braves    .408    25  Rockies    -3.834
 26  Mariners  .409    26  Braves     -3.984
 27  Rockies   .422    27  Mariners   -5.908
 28  Pirates   .423    28  Rangers    -6.856
 29  Reds      .423    29  Reds       -9.090
 30  Rangers   .424    30  Pirates   -10.697

2007
Rank Team     SLGBIP  Rank Team        PASBP
  1  Blue Jays .364     1  Red Sox     9.333
  2  Red Sox   .378     2  Blue Jays   7.201
  3  Padres    .379     3  Cubs        6.541
  4  Cubs      .382     4  Rockies     4.333
  5  Nationals .384     5  Indians     3.480
  6  Mets      .388     6  Braves      1.946
  7  Braves    .388     7  Orioles     1.635
  8  Orioles   .392     8  Giants      1.601
  9  Rockies   .393     9  D'backs     1.405
 10  Cardinals .394    10  Nationals   0.851
 11  Indians   .394    11  Tigers     -0.129
 12  Athletics .395    12  Rangers    -0.408
 13  Tigers    .396    13  Mets       -0.850
 14  Dodgers   .397    14  Cardinals  -1.081
 15  Yankees   .397    15  Padres     -1.247
 16  Twins     .398    16  Royals     -1.983
 17  D'backs   .398    17  Dodgers    -2.104
 18  Rangers   .402    18  White Sox  -2.115
 19  Giants    .403    19  Yankees    -2.230
 20  White Sox .404    20  Twins      -2.658
 21  Angels    .405    21  Phillies   -2.947
 22  Astros    .407    22  Marlins    -3.035
 23  Phillies  .407    23  Angels     -3.063
 24  Brewers   .415    24  Astros     -3.504
 25  Royals    .418    25  Athletics  -3.850
 26  Pirates   .418    26  Brewers    -6.378
 27  Reds      .418    27  Reds       -6.753
 28  Mariners  .420    28  Mariners   -7.655
 29  Marlins   .426    29  Pirates    -8.666
 30  Rays      .441    30  Rays      -12.908

The biggest changes in evaluation of team defense's SLGBIP prevention in 2008 were the Padres' dropping from fifth way down to 19th, with the Royals jumping up from 17th to sixth, and the Marlins moving from 14th all the way up to an impressive third place in PASBP. The biggest differences in 2007 were that the A's fell from 13th to 25th and the Padres fell from third to 15th, while the Giants climbed up from 19th up to eighth.

Comparing 2008 to 2009, we see several teams whose PASBP changed significantly. The Mariners went from 27th to first in SLGBIP in just one season. The Reds jumped from 29th all the way up to fifth, the Rangers from 28th to sixth, and the Rockies went from 25th to eighth. The Brewers plummeted from eighth down to 25th, the Mets tanked from 11th to 26th, and the Orioles went from ninth to 22nd. There were some real changes in PASBP in this past year, as four of the bottom six teams from 2008 found their way into the top ten teams of 2009.

The transition from 2007 to 2008 saw fewer changes, but the Rays did rise from dead last in 2007 to fifth in 2008, while Colorado fell from fourth to 25th. The Braves also fell, from sixth to 26th, but the Brewers rose from 26th to seventh and the Marlins went from 22nd to third. Many of those teams did regress back in 2009, but the Rays did manage to have an 11th-ranked PASBP after their huge jump from 2007 to 2008, and the Marlins stayed up at ninth in 2009. The Rockies went back up to eighth after their decline, while the Braves stayed down, only ranking 24th in 2009. The Brewers' ascension was nearly completely reversed, going all the way back down to 25th.

It appears that including this type of information is important. Although Slugging on Balls in Play is a useful statistic to evaluate team defense, it is probably more susceptible to park effects. Doing this kind of adjustment appears to have focused the analysis and improved the evaluation of team defense. Even after accounting for team defense in 2009, it is clear that the Mariners and Giants both played extraordinary team defense this year, especially in the outfield. As both clubs were not strong in team defense in 2008, this raises a lot of questions, especially in light of the sudden lack of persistence in team defensive rankings. Recall that last week I explained that Defensive Efficiency in 2009 had a negative correlation with 2008, the first time this has happened in the Retrosheet era. In fact, this lack of persistence appears to be consistent with respect to slugging as well: the correlation between 2007 and 2008 PASBP was .41, but the correlation between 2008 and 2009 was positive, but only .09. It is certainly notable that, defensively, baseball is changing rapidly as more information becomes available. Looking at all of these metrics throughout the 2010 season will be interesting and enlightening as we try to figure out what is happening in the game.

Matt Swartz is an author of Baseball Prospectus. 
Click here to see Matt's other articles. You can contact Matt by clicking here

Related Content:  Defense,  Marlins Park

23 comments have been left for this article. (Click to hide comments)

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willsharp

Great information, Matt.

The acronym is so close to "PABST". Can we change the wording around?

Oct 19, 2009 10:15 AM
rating: 2
 
MHaywood1025

Matt, I enjoyed reading this article, as I have all of the defensive-minded articles so far. Defense as a whole has been the unicorn of baseball analysts.

The one thing I am unclear on is why we use a teams home-road splits to determine their home park factor. Because they don't play in every stadium, can a teams home park factor be unfairly weighted based on the selection of parks they play in that year?

To me, it would make more sense to compare a teams home stats to a "neutral" park, possibly by averaging the number of singles, doubles, triples, and home runs hit in all of the parks for that year.

Oct 19, 2009 10:17 AM
rating: 0
 
BP staff member Matt Swartz
BP staff

Good question. I spent a while thinking about how best to do this, and ultimately reverted to the method used when James Click created PADE. I'm not sure that this is the best way at all, and I welcome suggestions, but in his article, Click expressed a concern that an extraordinary player might bias the factors significantly if it were done in a more traditional way, so Keith Woolner suggested using this method. If it works less for adjusting SLG on BIP, I'd be curious why and what good suggestions are for improvement. I'm not totally sold on the method at this point, but it seemed like a reasonably unbiased way to at least get the ball rolling on this.

Oct 19, 2009 10:29 AM
 
Ira

I have a different question about this. It seems that this can have biases based on the g/f ratio of the staff. A staff that forces players to hit th ball on the ground more would have lower slg than on which allowed more flyballs, some of which would turn into either ttoubles or triples.

Ira

Oct 19, 2009 10:37 AM
rating: 0
 
BP staff member Matt Swartz
BP staff

When you exclude home runs, SLG is actually slightly lower on fly balls than ground balls (.239 vs. 257).

Oct 19, 2009 11:05 AM
 
Ira

I do understand that, though I'm sure the shapes are quite different for rates of outs, singles, doubles, and triples in ground balls vs fly balls, with a huge number of ground ball singles and ground ball outs, a few groung ball doubles and a very few ground ball triples vs fly balls, which will contain lots more outs, some doubles, a few triples, and many fewer singles than the ground balls. of course we also know that balls in play can be split much more finely than grounders and fly balls. You have bunts, grounders, pop ups, line drives and fly balls. Ignoring triples for a moment (since their rate is very low), I would guess that the majority of doubles would be on fly balls, with most of the rest on line drives, small numbers on ground balls and negligable amounts on pop ups and bunts.

It seems to me if you are trying to evaluate outfield defense, you might start with the overall rate of doubles (and triples)hit to the outfield and then add in park factors and then start looking into park factors.

Oct 19, 2009 12:19 PM
rating: 0
 
BP staff member Matt Swartz
BP staff

So to make sure I understand you correctly, you're thinking that a good metric would be ISOBIP? or XBH/BIP? It's an interesting thought.

Oct 19, 2009 12:32 PM
 
sandyk

I very much enjoy this work, Eric. One concern that I have is that incorporating park effects in the case of extreme parks may have the effect of overstating (e.g., Red Sox and Rockies) or understating (e.g., Padres) the actual quality of defense. I am a little uncomfortable with the result that says that the Red Sox were best in this capacity over the 2007 and 2008 seasons (and by such a wide margin), especially given that they have had very poor play (by other metrics) from their left fielders during this time.

So, color me a bit skeptical of these results, even while I do think that taking into account the actual home parks is important.

Oct 19, 2009 10:37 AM
rating: 0
 
BP staff member Eric Seidman
BP staff

Matt and I may share the commonality of being Phillies fans, but I did not write this article :-).

Oct 19, 2009 10:57 AM
 
BP staff member Matt Swartz
BP staff

I certainly think that it's possible that this method may lead to biased results one way or the other, but I'm not sure I understand your argument why yet. It seems that your concern is how well the Red Sox placed. The Red Sox allowed 73% more doubles at home in 2008 than on the road, and they hit only 49% more doubles at home in 2008 than on the road. The allowed 59% more doubles at home in 2007 than on the road, and they hit only 19% more doubles at home in 2007 than on the road. So they certainly ended up with a very high park factor. I'm not sure whether this is wrong. Could you flush out this thought a little more?

Oct 19, 2009 11:19 AM
 
sandyk

Sorry about the slip, Matt! I guess all you Phillies fand look the same on the internet. :-)

My point was just that these rankings make it seem as though the Red Sox were MUCH better at taking away (mostly) doubles in the years 2007-2008, and were still third best in 2009, and these rankings seem at odds with other measures of outfield defense, which had Manny Ramirez and Jason Bay as dreadful for the Sox, and Ellsbury pretty bad this year.

Drew has graded out pretty well, though, and perhaps this is why the Sox rank so high? After all, most doubles to left and left center are due to the wall, while a good right fielder can make a very big difference in Fenway's huge expanse out there. Coco Crisp was supposedly sensational by those other measures for 2007-2008, so that may have helped, too.

Nevertheless, I remain a little skeptical since this year's outfield defense seemed worse than average overall.

Oct 20, 2009 09:14 AM
rating: 0
 
Tim Kniker

Matt, interesting. As a Royals fan some of this is hard to stomach. My guess is what you are saying in regards to them which is as a team, they were consistently consider a bottom 5 defensive team (especially with the likes of Callaspo at 2nd, Butler at 1st, and "stuck-in-molasses" Guillen in the outfield). After watching probably 85% of the games in the 1st half of the season (before my ulcers kicked in), I couldn't imagine a team that was worse, so I'm a little nervous that the new method puts them roughly at average. Granted after Guillen went down such that their outfield was typically DeJesus-Maier-Anderson/Bloomquist maybe it really was an average defense.

Oct 19, 2009 11:58 AM
rating: 0
 
BP staff member Matt Swartz
BP staff

Well, the Royals defense is terrible, but it's their infield defense that has really been the culprit, I think. Their UZR, at least, among outfielders is pretty close to average. But they are near the bottom of the league in every infield position. In general, this method is meant to be looked at alongside PADE to get a sense of both how well the defense records outs and how well they prevent extra-base hits. The extra-base hit prevention is more of an outfield thing, it seems. Is the Royals outfield defense really terrible, too, in your viewing experience?

Oct 19, 2009 12:31 PM
 
ragerd

Matt - any way to make those adjusted SLG's look like SLG %'s?

Oct 19, 2009 12:41 PM
rating: 0
 
BP staff member Matt Swartz
BP staff

Do you mean SLG without home runs? I guess I could think about how to do that. It would probably have a similar distribution to the unadjusted SLG but with smaller standard deviation, I think.

Oct 19, 2009 12:48 PM
 
havybeaks

How does PASBP compare with PABBP (park adjusted BABIP) as well as PABBP vs BABIP? Along with the PASBP vs SLGBIP you've shown above, such a comparison might shed some light on any park factor peculiarities.

Oct 19, 2009 13:15 PM
rating: 0
 
Ben Jedlovec

Matt- don't beat yourself up over the Mariners' radical movement in your rankings. They have admitted to going all-out to improve the team's defense this year, and the roster has largely turned over. Last year's weak defensive players were replaced with some of the best at each position (Wilson for Betancourt, Hannahan to supplement Beltre at 3B, Gutierrez and Chavez to go with Ichiro in the OF). Very similar story in Texas (Andrus/Vizquel/Jones) and Cincy (Bruce/Stubbs/Janish+ no more Adam Dunn). And the 2008 Rays.

Lineup turnover is clearly a large part of the year-to-year variance you're seeing. You'll want to find another way to evaluate your team ratings.

Oct 19, 2009 13:57 PM
rating: 0
 
BP staff member Matt Swartz
BP staff

Oh, I've been noticing the Mariners radical movement a lot! My last article was about the jumbling of defenses in the past offseason-- it was the first time in the retrosheet era (1954-now) that DE had a negative correlation with previous year DE. The Mariners were a big part of that, as were a few other teams who have focused on defense. Very interesting stuff!

Oct 20, 2009 07:44 AM
 
brslart

The consistently high ranking of the Cubs in these lists seems somewhat at odds with their wildly fluctuating team aggregate UZR over the same period. I'm not sure what that means, but I'm guessing that a good explanation of it would provide insight into quite a few things.

Oct 19, 2009 14:40 PM
rating: 0
 
BP staff member Matt Swartz
BP staff

The thing about defensive rankings is that there is always a lot of difficulty in measuring defense, so you want to look at several of them. The Cubs' OF had pretty good UZR in 2007 and 2008, but not as high-ranking as PASBP has them. The reason that the Cubs park factor is particularly helpful to their ranking is that they are particularly vulnerable to surrendering extra-base hits on balls in play at home, and much stingier on the road. I'm not sure if that's a skill that is being revealed here, or a bias. I'd be curious what Cubs fans had to say about watching fielders at Wrigley day after day.

Oct 20, 2009 14:34 PM
 
BurrRutledge

Nice work, Matt. Definitely useful alongside PADE. If given the choice, I think I like the idea in the comments above regarding a slightly modified version of this, to create a Park-adjusted ISOBIP statistic as PADE's complement.

For what my opinion is worth.



Oct 19, 2009 18:13 PM
rating: 0
 
McNulty

I'm stuck at work, its 4am, so forgive me if any of this is ridiculous, wrong or blatantly obvious.

This is kind of backwards from your article, but wouldn't a good way to take out Park Adjustment factors be to find out the SLGBIP on the road? The variety of parks throughout the league would provide a good normalization, no?

Oct 20, 2009 01:02 AM
rating: 1
 
BP staff member Matt Swartz
BP staff

Well, road SLGBIP would be interesting but like any road split, it lowers sample size to remove park effects. Using a park factor that is equal to the ratio of SLGBIP at home and on the road through the last three years is a way of getting most of the information embedded in home SLGBIP into the ranking. In other words, by looking at home/road SLGBIP splits over three years, you can get a better sense of how to view the home SLGBIP number for 2009 and use a larger sample size to evaluate this.

Oct 20, 2009 07:46 AM
 
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