Petco Park revisitedby Geoff Young
February 17, 2010
My first ever article here at Hardball Times examined the effects of Petco Park and how its home team, the San Diego Padres, might better take advantage of it. Now that we have three more years worth of data to work with, I thought it might be time to revisit this question.
We know that Petco Park is a pitchers' park, but let's take a closer look at the shape of its bias. The following tables (derived from data at ESPN.com) will serve as a reminder of just how extreme the environment in San Diego is, and also that in spite of this, there are periodic fluctuations. I've added hits and walks this time around for the sake of completeness. In the tables that follow, values higher than 1 favor the hitter, while values below 1 favor the pitcher.
That is some kind of consistency. Petco Park has been the least favorable environment for scoring runs in MLB for four of its six years in existence, finishing as runner-up the other two seasons. The scary thing is that even after it had established supremacy in that regard, the park managed to become stingier.
In 2009, the next lowest scoring environment, Cleveland's Progressive Field, checked in at .838, a full .097 ahead of Petco Park. The gap between those two parks is much larger than that between Coors Field and Chase Field last year (.054) at the top. Here are the gaps between Petco Park and the No. 29 ballpark over the past three seasons:
|Year||Petco Park||No. 29||Gap|
As a run suppressant, no other environment compares. This is why, if you're Jon Garland hoping to cash in on one final multi-year contract, taking a little less money for a short-term deal in San Diego makes sense in terms of re-establishing value on the open market.
One of these seasons—2006—sticks out like the proverbial sore thumb. At the time, I posited a couple of possible explanations for this shift:
- Buildings constructed beyond the outfield have changed wind patterns that may have kept more balls from leaving the yard;
- Pitchers have grown accustomed to the way Petco Park plays and are more susceptible to making mistakes high in the zone because they believe—consciously or otherwise—they can get away with it
I neglected to mention a third possibility, which, with the benefit of hindsight, appears to have been the correct one: The spike was anomalous. This leaves unresolved the question of why, but for whatever reason, the Padres and their opponents hit more homers at Petco Park in 2006 than they had before or have since.
Note in particular the home runs allowed by Padres pitchers in 2006 and 2007. They surrendered twice as many in the former as in the latter. Take the average of those two years and you get 68.5, which is in line with the surrounding seasons. It's almost as if the universe, seeking equilibrium, forced Padres hurlers back toward the mean. That's nonsense, of course, although I'd be lying if I claimed to have a better explanation.
Again, Petco Park consistently ranks at or near the bottom in terms of hits. It has been stingier over the past three seasons than the previous three, when it was already one of the most unforgiving in all of baseball.
The first two seasons downtown were pretty extreme, and then things got downright ugly in 2006. That is the year the fence in right-center was moved from 411 feet to 402 feet, which theoretically could reduce the area available for hitting doubles. That the lower park factor has held for four years running lends further support to this hypothesis. Whatever the reason, Petco Park is where doubles go to die.
Triples have been harder to come by lately as well. Part of this could be due to the change in dimensions previously mentioned, although the shift has been much more dramatic with triples, which suggests a few other possibilities:
- As Petco Park matures, teams are getting a better feel for how it plays and doing a better job of positioning their outfielders to minimize the likelihood of triples.
- Triples are a comparatively rare event and therefore more subject to random fluctuation.
- Some other factor(s) I haven't considered.
The suggestion of randomness holds great appeal to me in general because in my experience, people often ascribe meaning to events that have none. However, the fact that the movement has been consistent and steady in one direction leads me to wonder: Do other venues fluctuate so much?
Well, yes, some of them do. The Texas Rangers' home park, for example, went from 1.840 in 2005, to .780 in 2006, to 1.650 in 2007, to 2.230 in 2008. That's a lot of movement.
But in terms of heading in one direction, no other ballpark in MLB has seen a consistent decrease (or increase) in triples from year to year over the period 2004-2009. Detroit's Comerica Park comes closest, having its steady decline (1.840, 1.760, 1.170, 1.600, 1.110, 1.080) interrupted only by a spike in 2007. At the other end of the spectrum, the Florida Marlins' home park had been becoming increasingly triples-friendly (1.030, 1.110, 1.410, 1.460, 1.480) until last year, when the bottom fell out (.640).
Right now I'm inclined to classify Petco Park's downward movement as intellectually interesting but difficult to explain and of questionable impact. Still, it bears watching.
This is all over the place, and I have no idea why. What is interesting to me is that there is a lesson here in misusing statistics. Had we looked at this after the 2007 season, we might have concluded that because the ball doesn't carry at Petco Park and it's easier to get away with mistakes, pitchers aren't afraid to attack hitters, leading to fewer walks. However, someone looking only at last year's data might reach the opposite conclusion and assume that because it's easier to get hitters out at Petco Park, pitchers aren't afraid to put someone on base every now and again.
The truth is, we don't know (perhaps Adrian Gonzalez and the lack of fearsome hitters around him in the lineup are to blame?). It's an oddity in the record, but I'm not prepared to imbue that oddity with meaning just yet.
The bigger picture
Finally, we return to the question I asked three years ago: "Were the Padres able to use any of this to their advantage?" One way of looking at this is to compare their expected (Pythagorean method, 1.83 exponent) record with their actual record at home:
Thomas Thress has shown (By the Numbers, May 2004, p. 19) that there is a bias in this approach, noting that "from 1900 through 2003, the Pythagorean Theorem underestimated the number of home wins for 72.8 percent of all teams." Thress continues by explaining why this is so:
When the home team wins a game, they bat in fewer innings than the visiting team. In most cases, the home team will not bat in the bottom of the ninth inning. Hence, they have one-ninth fewer opportunities to score than the visiting team.
This is something I had failed to consider in my original analysis. Worse, I'm no longer certain that we're asking the right question here.
The Padres have outperformed their Pythagorean at home by 21 games in six years (486 games total). According to Thress, teams typically outperform their Pythagorean at home by four games per 162, so we would have anticipated something more along the lines of 12 extra home wins. In other words, the Padres have won about nine more games than expected at Petco Park during its existence. That comes to 1.5 wins per 162 games, or three-quarters of a win per 81 games (the number of home dates in a season).
There are two problems I have at this point. First, how much difference does less than one win a year make? I mean, so what if the Padres have won nine more games than expected over six seasons? That's not a lot of extra wins, and it's quite possible that luck is the overriding factor in the difference between expected and actual total.
Second, even if there is some skill involved in improving one's home record by a microscopic amount in any given season, does this necessarily signify that the team is taking advantage of its park? I'm not sure it does. What might be better to study—and I'm not going to do it here due to space considerations and because I haven't thought this through yet—is the difference between home winning percentage and road winning percentage as compared to that same difference for other teams.
Petco Park remains the most difficult environment in MLB in which to score runs, and by a wide margin. It appears to have gotten even more difficult beginning in 2007. It has consistently killed hits, doubles, and homers (except for the anomalous 2006 season, when Padres pitchers coughed up an extraordinary number of home runs).
Perhaps most interestingly, Petco Park apparently has gone from a place that initially yielded a lot of triples to one that suppresses them. Why this is the case and whether the current trend will continue remain unknown. Also curious is the yearly fluctuations in walks. In 2007, Petco Park yielded fewer bases on balls than all but two other parks in baseball; in 2008, it was middle of the pack; and last year, it became a walking man's paradise.
The question of whether the Padres are using Petco Park to their greatest advantage remains open. This may be worthy of additional study.
References and Resources
ESPN park factors
Geoff Young covers the San Diego Padres at Ducksnorts and is a contributor to Baseball Prospectus. Feel free to send Geoff comments via email.