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.
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The acronym is so close to "PABST". Can we change the wording around?
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.
Ira
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.
So, color me a bit skeptical of these results, even while I do think that taking into account the actual home parks is important.
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.
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.
For what my opinion is worth.
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?