Home Field Disadvantage
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by user DNL
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| more "on the DL" opinions |
About a week ago, David Pinto posed an interesting question. It turns out that, through mid-June, the Philadelphia Phillies had hit 76 doubles at home while giving up 77. On the road, they hit 46 while giving up 70. Why had the Phillies' doubles seemed to disappear on the road? Pinto wondered, "Do the batters get into bad habits in that ballpark because power is easy there?"
Balls Sticks and Stuff reposted the excerpt (indeed, that's where I first noticed it), and added this: "As I recall, the doubles rates have always been low at Citizens Bank Park while the homerun rates have been high. I've always assumed it was because what would be a double at most parks was a homerun at CBP. But if the Phils give up the same number of doubles away as they do at home, then that hypothesis doesn't hold."
So, what gives? Maybe Pinto is right -- maybe it's bad habits causing the change. But I think there's more than just habit causing the issue. It may be psychological. Here's the bare-bones reasoning:
- Power is easy at Citizens Bank Park.
- Hitting for power is a good thing if you're a hitter. That is, we can use "power" as a proxy for success, at least as an individual batter is concerned.
- Relatively speaking, a Phillie, by virtue of the fact that he regularly plays at CBP, is going to find it more diffult to hit for power away than he will at home.
- Therefore, a player who suddenly struggles may very well continue to struggle -- that is, difficulty causes further difficulty.
- A non-Phillie, by virtue of playing games at CBP, is more likely to be successful than not, due to ballpark effects (excepting teams that also play in hitter-friendly parks)
- Therefore, a player who suddenly improves may very well continute to improve. We call it "getting off the schneid."
If that's true, the data should bear it out. Let's start with the Phillies, using an expanded version of Pinto's data set.
All data is courtesy of Pinto's invaluable Day-by-Day Database.
Philadelphia Phillies, XBH Splits, 2006 season through June 18, 2006
| Home | Away | Ratio | |
| Home Runs Given Up | 54 | 30 | 1.8 |
| Home Runs Hit | 51 | 42 | 1.2 |
| Triples Given Up | 7 | 8 | .9 |
| Triples Hit | 7 | 4 | 1.8:1 |
| Doubles Given Up | 86 | 70 | 1.2 |
| Doubles Hit | 81 | 46 | 1.8 |
| Total XBH Given Up | 147 | 108 | 1.36 |
| Total XBH Hit | 139 | 92 | 1.51 |
This isn't dispositive of anything, but it is interesting to see a few things. First, the Phillies and their opponents are rather similar at CBP -- both have about 52 homers, both have 7 triples, both have about 83 doubles. While this doesn't take into consideration opportunities (noting that the Phillies lose three outs for home wins, for example, or differences in OBP), it is at least demonstrative.
On the road, however, the Phillies have significantly more homers but overall, fewer extra-base hits. It makes sense that the Phillies have more road homers than other teams, as guys like Ryan Howard, Bobby Abreu, and Pat Burrell can pretty much clear the fences in any park. Any it may, potentially, make sense that the Phillies have more doubles at home than on the road for a similar reason, as David Bell, Jimmy Rollins, and the flavor-of-the-month CF and catcher aren't huge threats to go yard anywhere. Therefore, maybe the benefit they get from CBP is an increase in doubles. That doesn't necessarily make sense, though, as it shouldn't really be easier to hit doubles at CBP than, say, Shea Stadium or RFK.
The data suggests that the Phillies are, indeed, not benefiting from their ballpark any more than their opponents are, while simulataneously suggesting that the Phils are being harmed by opposing ballparks more than their opponents. The data set has a number of flaws, and looking at rate numbers -- specifically, OBP, SLG, and OPS -- should be more instructive.
Philadelphia Phillies, OPS Splits, 2006 season through June 18, 2006
| Home | Away | |
| Given Up | .356/.486/.842 | .334/.435/.769 |
| Produced | .336/.462/.798 | .327/.408/.735 |
The average Phillie loses 63 points in OPS when he leaves home. That's a decrease of almost 8%. Incredibly, the average opponent loses even more points -- 73 -- when he leaves CBP; a decrease of about 8.5%. That suggest that Pinto's hypothesis is wrong to some degree. It can't be merely bad habits that the Phillies are demonstrating. Relatively speaking, the Phillies drop off less than their opponents do. (Pinto's hypothesis isn't entirely incorrect -- some of the effect can and probably should be attributed to "bad habit" or similar issues.)
But there's more here. First, there's the temporal issue. The "produced" numbers reflect the Phillies bats as a team. Therefore, each of the players putting up those numbers (with few exceptions: trades, releases, DL stints, options, etc.) will have both recently played at CBP and will soon return there. The CBP effect is recent in their minds and their muscle memory. This is most certainly not true for the Phillies opponents on the whole. So the "change" from CBP to another stadium should be less of an issue, at least in regard to psyche and habit and that stuff.
Second, the "Produced"/"Home" line is high, but it's not astronomically so. Indeed, it's basically what one would expect (albeit on the high end) from a hitter-friendly ballpark effect. But that "Given Up"/"Home" field is, well, sick. At CBP, the average Phillie opponent looks a lot like Johnny Damon (minus the speed), who has a .359/.470/.829 to date. That's crazy talk, especially considering that pitchers are included in that data set. I mean, could you imagine a lineup, one through nine, of guys who hit like that?
So, what gives? I think it's the above-mentioned positive effect on a batter's psyche. I leave it to others to find hard data that suggests that I'm either right or wrong. But here's some anecdotal evidence.
A guy is mired in a pretty bad slump, getting a piece of pitchs but not enough. Hits are turned into pop-ups; gappers cut down as singles; homers into long flyouts. Suddenly, a factor is introduced that helps him a bit. Would you expect this to have a positive effect on his hitting, beyond the effect of the newly-introduced factor?
Looking at Carlos Delgado's seaosn to date, it's really not surprising that a seven-game stretch in Arizona and at CBP was good for his three week slump. His OBP went from .339 to .352. His SLG shot up from .496 to .542. Pretty crazy numbers. Obviously, not all of that is ballpark effect, and it's also helpful that he started off at below his normal pace. But again, anecdotal evidence would suggest that all he needed was a push.
Can we do better than that? Probably. What about the bandbox of them all: Calorado? If the effects I suggest exist, they should be on display there.
Colorado Rockies, XBH Splits, 1995 season through June 18, 2006
| Home | Away | Ratio | |
| Home Runs Given Up | 757 | 555 | 1.4 |
| Home Runs Hit | 669 | 473 | 1.4 |
| Triples Given Up | 147 | 105 | 1.4 |
| Triples Hit | 181 | 96 | 1.9 |
| Doubles Given Up | 1122 | 1010 | 1.1 |
| Doubles Hit | 1126 | 887 | 1.3 |
| Total XBH Given Up | 2026 | 1670 | 1.21 |
| Total XBH Hit | 1976 | 1456 | 1.36 |
The Rockies have been playing at Coors Field since the start of the 1995 season. The above is the Rockies' data from that point to present (well, June 18th), and again from the Day to Day Database.
Again, we see the team in question doing proportionally better at home than on the road, when compared to their opponent, and substantially so.
Of course, aggregation stats aren't as good as rate stats. So, to the percentages!
Colorado Rockies, OPS Splits, 1995 season through June 18, 2006
| Home | Away | |
| Given Up | .365/.491/.856 | .348/.438/.786 |
| Produced | .377/.505/.884 | .313/.384/.697 |
What's most interesting here is that the Rockies player is much better than the non-Rockie while playing at Coors, but when not at Coors, he's much, much worse. Night and day worse. I think Pinto's "habit" argument explains most of it -- at Coors, free-swinging is not a bad idea. But if you keep doing that at other places, it's going to mean a lot of extra outs that'd otherwise be walks (or better pitches to hit).
However, there may also be a large psychological component. At some point, a Rockies player -- putting up that paltry .697 OPS -- has to start thinking that he can't succeed outside of Coors. Then, when he gets home, he's on fire -- .884 OPS. For perspective, coming into the 2006 season, Jose Reyes had a career .698 OPS, while Rafael Palmeiro put up an .885. We're talking more than just habit, here.
Again, the analysis can't end there. There's another question.
Does it Matter?
Let's say that Pinto and I are right -- that players in offensively-friendly home ballparks tend to have significant falloffs when on the road; moreso, in fact, than we can attribute to the ballpark's effect itself, be it bad habits and/or psychological issues. Why should we care?
In the case of the Phillies, the effect truly is not all that bad. There's a falloff, but as noted, it's actually not as bad as it is for the opponent. If anything, the numbers suggest that the Philles do not benefit from being at home as much as their opponent benefits from CBP.
In the case of the Rockies, that's simply not true. At home, they put up an .887 OPS and face an .854 OPS at Coors. That means a lot of high-scoring but otherwise close games. The advantage is theirs, but it's probably slight.
However, if this gain results in their road numbers, then the victory is a Pyrric one. The .786 OPS they face on the road, while putting up a meager .697? That's a recipe for slaughter. In essense, their home field advantage because a negative, as it causes them much in the way of ills elsewhere.
In effect, home field is a disadvantage.
Date
Mon 06/19/06, 11:21 am EST
