Park factors: Home quirks play into roster strategy

Metric compares teams' stats at home vs. road to determine how stadiums play

Park factors: Home quirks play into roster strategy

As the ever-evolving statistical analysis of baseball grows and gets more enlightening -- and often confusing -- with every added integer and discernible piece of data, there's always a comfortable place to land.

That would be the place where you sit down in plastic chairs with a beverage in hand, popcorn and hot dogs at the ready, and the wondrous doings of big leaguers played out in front of you 162 games a season.

Major League ballparks are so impressive that some people spend their entire summer and much of their bank accounts visiting all 30 in the same summer. Some of the more eccentric of these folks even do it by bicycle.

And they might not realize it, but aside from quirks such as the Green Monster in Boston, the B&O Warehouse in Baltimore, Monument Park in the Bronx, the multicolored home run sculpture in Miami and the ivy on the walls of Wrigley Field, they're witnessing a valuable statistical key to player performance every time they go through the turnstiles.

It's called "park factor," and while its formulas are difficult to explain, they're all adding up to something significant. Teams are constructing rosters and making up lineup cards with stadium effects in mind, and this figures to only become more common over time.

In Seattle, for example, the spring nights are still chilly and the damp Puget Sound air isn't making Safeco Field a party for hitters. However, the Mariners had spent more than a decade watching park factor numbers prove that the stadium was on the extreme side of things as a venue friendlier to pitchers than hitters, so the team moved in the outfield fences -- most significantly in the "Death Valley" of left-center field -- and it's now playing more neutral.

"All we were trying to do is make our park a fair park," Mariners general manager Jack Zduriencik said. "We wanted to take away the psychological effect, as well as the actual distances the fences were. We noticed we'd go to Cincinnati, to Coors Field [in Denver] and to Texas, and our guys loved it.

"So we made the changes, and last year, we were among the league leaders in home runs. It was a big jump. Now, some of that had to do with personnel, and I think that our players are more mature. They were another year older. But certainly bringing in the fences has taken the negative edge away from the hitters. It's still very fair, though. We don't hear pitchers complaining either."

So far this season, some of the usual suspects appear to be the most hitter-friendly. Coors Field leads the pack, according to ESPN.com's park factor rankings, and has since 2008. Interestingly enough, however, Miller Park in Milwaukee is the most pitcher-friendly in the Majors so far this season, a stark contrast to last year, when it ranked fourth, according to ESPN, with a park factor of 1.081 (1.000 being neutral).

Safeco, meanwhile, scored a .831 on ESPN's scale in 2012, making it by far the most pitcher-friendly park in baseball, and then jumped to a slightly hitter-friendly 1.008 in 2013 after the dimensions were changed. This spring, the Seattle weather has been cruel on baseball players and fans in general, which has carried over to the hitters. Safeco ranks 27th in baseball at .893, but don't necessarily expect that to continue. As the weather warms up, so should the bats, according to Greg Rybarczyk, a baseball-operations analyst for the Boston Red Sox who developed the Hit Tracker Online, which was licensed to ESPN.

"It's early," Rybarczyk said. "It's been a cold April. Maybe it's a bit too soon to draw conclusions, because it hasn't been a typical season, weather-wise."

Rybarczyk said one thing you can bank on, though, is that park factor in baseball ends up being a pretty useful tool, because the game and its fields of play are so unique.

"It is the one characteristic different from the other sports," Rybarczyk said. "Football and basketball are played in uniform-sized venues, and baseball is not. So it can have influence on the games."

It can have influence on signings, too. The Twins, for example, were willing to take a closer look at free-agent right-hander Phil Hughes, who had a 4-14 record and a 5.19 ERA for the Yankees in 2013, giving up 24 homers in 145 2/3 innings. Seventeen of those homers were surrendered in New York, which, according to fangraphs.com's 2013 park factors by handedness, ranked tied for second in the big leagues at 114 (with 100 as neutral) for hitter-friendly parks on home runs by left-handed hitters.

The Twins liked Hughes' age (27) and his mid-90s fastball. They also liked the fact that their park, Target Field, scored an 89 on the same scale. They gave Hughes a three-year, $24 million contract, and he's 4-1 with a 3.90 ERA so far this year.

"You look at players' numbers, and you want to make sure they're not a factor simply because of where they play," Twins assistant general manager Rob Antony said. "Phil's a glaring example.

"You look at it and say, 'Our park is much more conducive to a fly-ball pitcher than Yankee Stadium.' And it makes sense. You look past some of the other numbers, because you're looking a little deeper.

"I think every club does that."

Doug Miller is a reporter for MLB.com. Follow him on Twitter @DougMillerMLB. This story was not subject to the approval of Major League Baseball or its clubs.