Park Effects, Schmark Effects

Dave Paisley

A few weeks ago I checked into park effects and showed how teams take varying advantage of their home parks. I've never been a fan of one year park effects and today I hope to show you part of the reason why.

Don't get me wrong -- park effects are real. But it is possible to read too much into what is mostly random variation, especially in single-year numbers. I'm going to use San Diego as an example here.

First, park effects are usually quoted as factors derived from runs scored in a particular park. That's OK, but run scoring is the final event that results from offensive production. Given the same OPS generated in two parks, there could be quite different numbers of runs scored from what is essentially the same offense, so I see it as cleaner and more accurate to use OPS to derive park effects.

Taking a look at San Diego in 1998, the runs scored park factor was 75, meaning for every 100 runs scored in games at other parks, only 75 would be scored by both teams at Qualcomm. That's pretty radical, as Dodger Stadium has generally been regarded as death on offense, and it's averaged about 84 for the last four years. Qualcomm had an RS park factor of 92 in 1997 and averaged 90 for the years 95-97, so a drop to 75 is pretty radical.

Now here are the numbers based on OPS for the last two years:
 

Year	Pads  at Home	Pads on Road	Opponents  at Qualcomm	Opponents  at  Their Parks	Park  Factor
1997	.726	.772	.758	.816	93.5
1998	.706	.769	.616	.782	85.2

It's interesting to note that in 1997, the ratio of the Padres home/road splits was about the same as that of their opponents. There's no doubt that Qualcomm suppresses offense, but 1997 wasn't terribly extreme.

Last season, however, was completely different. The Padres numbers were quite similar to '97, maybe a little worse, but the home/road split was similar. Their opponents, however, were vastly different. Overall, the Padres' pitching was much more effective, primarily due to the addition of Kevin Brown, but the drop in their opponents offense in Qualcomm is massive. A .616 OPS for the season for their opponents is tantamount to a massacre, and is totally unprecedented. It certainly is anomalous with past seasons.

Looking for reasons, I pulled out the splits for the Padres' primary pitchers in '98. The "Home" and "Road" numbers are opponents' OPS against that pitcher:
 

Pitcher	Home	Road	Personal Park Factor
Ashby	.685	.739	92.7
Brown	.509	.639	79.7
Hamilton	.630	.883	71.3
Hitchcock	.593	.870	68.2
Langston	.786	1.007	78.1
Hoffman	.474	.446	106.3

And then for 1997. Kevin Brown pitched for the Marlins in '97, of course, so his numbers aren't totally relevant, except to note that he does appear to like that home cookin'. (Lest you think that Florida was a pitcher's paradise in '97, the OPS park factor was 99, i.e., pretty neutral.)
 

Pitcher	Home	Road	Personal Park Factor
Ashby	.640	.749	85.4
Brown	.528	.593	89.0
Hamilton	.804	.706	113.9
Hitchcock	.694	.909	76.3
Langston	.866	.960	90.2
Hoffman	.629	.572	110.0

It's interesting to note that Brown took incredible advantage of Qualcomm in '98. Ashby took less advantage than in '97, while Joey Hamilton switched from much worse to vastly better at home. Sterling Hitchcock turned a large advantage into an even larger one while Mark Langston (who pitched for Anaheim in '97) was bad all around, but better at home. Trevor Hoffman is the only pitcher consistently better away from home. Not a bad attribute in a closer, being able to block out those opposing fans when you have to.

So between an extreme swing in Hamilton, the addition of Brown and a general trend toward better home pitching, San Diego became the place where visiting offenses go to die. Those factors drove the OPS park factor from 93 to 85, and the runs scored factor from 92 to 75.

The fact that the Padres' own offense remained relatively untouched through all of that is testament to the fact that one-year park factors, and especially those based on runs scored, don't mean squat.

Stay tuned for more stunning revelations in the weeks to come.

 

about the author

Dave Paisley's next stunning revelation will be that he secretly wears Yankees Underoos. Regale him with lingerie stories of your own at drdjp@strikethree.com.