Park Factors

March 10, 2010 1:28pm CST

In the fantasy game most of us keep an eye on which team a guy plays for. We also pay close attention to who surrounds that player in his lineup. However, this concern rarely moves into the realm of a discussion about a player's home park, except in a few cases (such as places like Coors Field). Hell, it used to be that drafting a pitcher from Coors Field was akin to poking a finger in your eye for fun, but even that has changed since they brought in the humidor to level the playing field (Ubaldo Jimenez being a prime example of that fact. You can read more about him here). Still, ballparks certainly impact a player's level of performance even if most of us don't inherently build that into our projections for players on draft day.

We all know that you shouldn't be overly excited about drafting a pitcher from Colorado or Philadelphia because of those parks' propensity to give up a lot or runs, but is that common belief supported by data or is it just anecdotal information that we have all grown to simply accept? What if I told you that in 2009 that Yankee Stadium, while a great venue for home runs, was actually slightly worse than average a place to score runs. Would you believe me?

With this article I will attempt to address this issue by focusing squarely on the impact that stadiums can have on player performance. In the first part of this article I will review how each park stacks up in relation to all others in its particular league. After showing you how the parks rate, I will spend a moment detailing a few of the players who switched teams in the offseason and address how their new homes might impact their performance this year.


2009 PARK FACTORS

Which parks are good hitter's parks? Which are good pitcher's parks? While general wisdom tells us places like Colorado are good for hitters, and parks such as PETCO Park in San Diego are good for pitchers, are these generalizations supported by the facts? I will address this issue by presenting to you the idea of Park Factors.

Park Factors put the stadium under the microscope to analyze whether or not it favors pitchers or hitters from a variety of angles. Here is the definition used by ESPN.

"Park Factor compares the rate of stats at home vs. the rate of stats on the road. A rate higher than 1.000 favors the hitter. Below 1.000 favors the pitcher. Teams with home games in multiple stadiums list aggregate Park Factors."

A Park Factors mark of 1.000 is average, or neutral.

A mark over 1.000 is good in terms of offensive production.

A score under 1.000 is not good for the offense.


In 2009, AT&T Park in San Francisco earned a 1.016 mark in doubles. This means that when compared to all other ballparks, it was .016 percent easier to hit a double at AT&T Park than it was in the other parks. Conversely, AT&T Park earned a mark of 0.970 in home runs, meaning it was three percent harder to hit a home run there than in other stadiums. That's a simple enough explanation, is it not?

With that brief explanation, here are the 2009 Park Factors for the two most important factors, Home Runs and Runs Scored.


Ballpark HR Ratios for the 2009 Season
1.000 = The League Average

Stadium	P.F.	Stadium	P.F.
Yankees	1.261	Phillies	1.005
Angels	1.220	Blue Jays	0.990
Rangers	1.194	Tigers	0.974
White Sox	1.193	Nationals	0.970
Orioles	1.185	Giants	0.970
Reds	1.176	Red Sox	0.964
Marlins	1.127	Rays	0.939
Twins*	1.111	Athletics	0.927
Rockies	1.082	Mariners	0.886
Brewers	1.069	Dodgers	0.876
Astros	1.065	Braves	0.861
NY Mets	1.057	Royals	0.761
Pirates	1.054	Cardinals	0.736
D'backs	1.042	Padres	0.721
Cubs	1.006	Indians	0.670

* Will be in a new outdoor stadium this season.

Clearly the place to be last year was in the new Yankee Stadium, which was by far and away the best place in baseball to hit a ball into the seats. Surprisingly, Disney Stadium, aka the Rock Pile, i.e. the place where the Angels play, was the second-best park. In third place was the paragon of offense in Texas, The Ballpark at Arlington.

On the downside, PETCO Park in San Diego actually wasn't the worst park in baseball to go deep in - it finished second from the bottom. The park in Cleveland was actually the worst, and by a decent margin. Third from the bottom is the ball yard in St. Louis, which has to make you even more impressed by what Albert Pujols does year after year.


Ballpark RUN Ratios
100 = The League Average

Stadium	P.F.	Stadium	P.F.
Rockies	1.247	Nationals	1.008
D'backs	1.193	Rays	0.996
Cubs	1.146	Reds	0.975
Marlins	1.136	Athletics	0.974
Royals	1.113	Yankees	0.965
Twins*	1.090	Mariners	0.947
Rangers	1.085	Mets	0.943
Red Sox	1.072	Blue Jays	0.937
White Sox	1.062	Astros	0.930
Giants	1.052	Cardinals	0.919
Orioles	1.037	Braves	0.895
Phillies	1.028	Brewers	0.886
Tigers	1.026	Dodgers	0.857
Pirates	1.022	Indians	0.838
Angels	1.020	Padres	0.741

Coors Field may not be the homer haven it once was because of the humidor, but it is still the best place in baseball to score runs. Another NL West park comes in at No. 2 in Chase Field. In fact, the top-4 parks on the list all are from the National League.

The toughest place to score a run last season was in San Diego, which is not a shock at all. The Dodgers park in third also isn't a surprise, as the park has always favored pitchers, but the fact that Cleveland and Milwaukee also finished in the bottom four is a bit shocking, is it not?


OFFSEASON PLAYER MOVEMENT

Listed below are a few of the players who will call new places home in 2010 and how that change of address might alter their production.

Jason Bay, Mets
Bay moves to a park that was 22nd in runs but 12th in home runs, which begs the question: What exactly went wrong with David Wright last year?

Adrian Beltre, Red Sox
Fenway was 8th in runs and 21st in homers last season, though it was first in doubles (1.370) a massive number, so even if he doesn't blast a bunch of homers cause of the yard, Beltre should produce a ton of extra base hits.

Marlon Byrd, Cubs
Byrd moves from the third best homer park to the 15th, which is not a good sign for a guy with only one 20-homer season in his career. Some of that loss could be made up in the runs category though as his new park is better for runs scores.

Johnny Damon, Tigers
Will Damon repeat his 24-homer outburst moving from the best homer park in baseball to the one that was 18th? Not likely.

Curtis Granderson, Yankees
Granderson goes from the park that was 18th in homers to the one that was first as the anti-Damon. Coming off a season of 30 homers, the future is bright - at least in the homer department.

Vladimir Guerrero, Rangers
Vlad goes from No. 2 to No. 3 in terms of homers, while moving up eight spots in runs. As long as he stays healthy, he should be good to go.

Roy Halladay, Phillies
The Phillies' ace will pitch his home games in a park that finished 12th in runs last season. Rogers Centre in Toronto was 23rd, but the difference could be negated by facing lineups that aren't nearly as deep.

Matt Holliday, Cardinals
Will get a full season in St. Louis at a park that was 25th in runs and 28th in homers. He'll need to ride the Albert Pujols wave to success.

John Lackey, Red Sox
Fenway is always a touch place to pitch if you give up flyballs because they have the nasty habit of turning into doubles.

Adam LaRoche, Diamondbacks
He's going to be loving life in the desert since his home park was 2nd in runs, 2nd in doubles and 14th in homers.

Cliff Lee, Mariners
Lee moves to the Pacific Northwest to a park that was 24th in runs and 23rd in homers. That's obviously good news.

Javier Vazquez, Yankees
As mentioned above, the park in New York decidedly favors hitters. Given Vazquez's problems at keeping the ball in the yard, he owns a career HR/9 mark of 1.16, it could be a rough transition back to the AL.



PARK FACTORS FORMULA

PF: ((homeRS + homeRA)/(homeG)) / ((roadRS + roadRA)/(roadG))

homeRS: Runs scored at home

homeRA: Runs allowed at home

homeG: Home games

roadRS: Runs scored on the road

roadRA: Runs allowed on the road

roadG: Road games