Impact of changes to Safeco, Petco

For a comparison point, within the past 10 seasons, two venues similarly had their outfield dimensions reduced: Comerica Park, home of the Detroit Tigers, following the 2002 season, and Citi Field, home of the New York Mets, before last season.

Quickly addressing the first, keeping in mind that some advanced metrics weren't readily available 10 years ago, there were 32 more runs scored and 139 more home runs hit in the three seasons following Comerica's changes (2003-05) than in the venue's first three years of existence (2000-02); and the Tigers and their opponents scored nearly identical run totals in either three-year subset, meaning strength-of-competition probably wasn't the primary influence. By moving in the fences by as much as 25 feet in certain spots (that specifically to left-center field), Comerica became considerably less pitching-friendly; it has ranked ninth, ninth and 17th in runs scored, and 17th, 14th and 18th in home runs, on our Park Factor page the past three years working backward, after ranking near the bottom in both in 2001-02.

The impact of Citi Field's changes, meanwhile, can be more easily measured thanks to increased statistical availability the past half-decade. One of the most pitching-friendly ballparks in baseball during its first three seasons of existence -- it was arguably the No. 2-such NL park to Petco -- Citi Field saw 24 more home runs hit there in 2012 than in any of the preceding three years.

For a better way to measure these changes, let's break down Citi Field's statistics into three categories, BABIP (batting average on balls in play), home run/fly ball percentage and isolated power (slugging percentage minus batting average), as well as by direction, left field, center field and right field (those defined as each span of 30 degrees working from the left field to right field foul lines).

The following two charts illustrate the impact of Citi Field's changes: The first shows the change in measurements; the second the venue's statistics from 2009-11 combined, under its previous measurements, and in 2012, under its new ones.

Specifically, the impact of that 13-foot decrease in fence distance, and eight feet in height, in left-center field boosted Citi Field much closer to league-average territory. Mets players hit 11 home runs to left-center at Citi in 2012 after hitting only four to that part of the park in 2011, and their home run/fly ball percentage rose, from 2.6 to 8.8. Frankly, if the Mets had more right-handed power hitters in their lineup -- David Wright and Scott Hairston were effectively their only two -- the impact might've been more evident. And that's the point: That seven-homer difference shows how minor park effects can sometimes be, while the Mets' limited righty power exemplifies how park effects have much to do with personnel. Heck, we might not even get a true read on how much Citi Field's new dimensions have affected things for a few more seasons, nor might it matter in 2013, anyway, as Wright and John Buck represent their only righty power bats.

It was the impact upon pitching that stood out: The Mets' team ERA at Citi Field was 4.02 and their home runs allowed per nine innings 1.08 in 2012, whereas their numbers at home in those categories were 3.65 and 0.75 from 2009-11. Mets pitchers did manage a higher quality-start rate there in 2012 (67.9 percent) than from 2009-11 (57.2 percent), but their opponents did not, managing a 43.2 percent rate in 2012, down from 46.9 percent the three years before it. In short, the prospects of matchups seeking dropped as a result of Citi Field's shrunken dimensions, albeit by a small amount. And with R.A. Dickey now in Toronto, one might assume the Mets' quality-start rate to exhibit a similar decline in 2013. Remember: Personnel.

Now, let's apply those lessons to Petco and Safeco.

Petco Park's changes

The problem with evaluating the changes at Petco is similar to that of Citi Field: The Padres are comparably weak in terms of personnel likely to exploit them. Though the fences moved in slightly in left-center field, the most substantial tweak is to the area in right and right-center field, where the fences will both be brought in 11 feet and lowered from 11 to eight feet. These are the modifications:

Even with those tweaks, Petco remains an extremely spacious venue, simply less cavernous. With the exception of the measurement to straightaway center field, every outfield dimension rates above the major league average -- you can see those in the charts further down -- and there isn't an ideal comparable among current major league parks. Marlins Park, home of the Miami Marlins, and Turner Field, home of the Atlanta Braves, are the two closest, and both of those venues rated among the 10 worst for home runs on our 2012 Park Factors page.

Chase Headley, a switch-hitter who hit 20 of his 31 home runs from the left side of the plate, is the most obvious individual Padre under fantasy owners' microscopes. Headley, however, hit 21 of those 31 total homers down the left- or right-field lines -- specifically the spans of approximately 18 degrees from either foul line -- and nine of his 13 at Petco down either line, showing more of a pull- than alley-power tendency. He also had a 20.5 home run/fly ball percentage, representing an increase of nearly 15 percent upon his 2009-11 combined number (5.9 percent), meaning some naturally regression in homers was likely anyway.

Petco's adjustments might alleviate slightly that regression, and perhaps Headley will adapt his game with the knowledge that the alley fences are shorter. Still, it's foolish to assume that smaller Petco dimensions might inspire a better 2013 than 2012; rather, they marginally improve his prospects at a repeat.

Meanwhile, Padres with more modest 2012 home run/fly ball percentages could pick up a little in the power department -- think 1-3 home runs apiece -- including Yonder Alonso (4.2 in home games), Cameron Maybin (5.0) and Will Venable (3.9). The most noticeable statistical change, however, will probably be upon pitchers -- just as discussed earlier with Citi Field in 2012 -- specifically those who relied more upon matchups than talent to succeed.

Padres starters Clayton Richard and Edinson Volquez, for example, had road ERAs more than a run and a half higher than at Petco, neither classifying as elite, top-of-the-staff types. Both, fortunately, are ground-ball types, meaning neither should be devoid of matchups appeal, but their number of useful matchups should nevertheless decline slightly in 2013. As for visitors to Petco, the shrunken outfield dimensions should make NL-only owners think twice about blindly streaming anyone scheduled there, especially with lesser-skilled, fly-ball pitchers like Travis Wood, Aaron Harang and Mike Fiers.

Safeco Field's changes

The Mariners, meanwhile, aren't that much more stocked with personnel to exploit Safeco's changes than the Padres, with one key difference: Safeco's adjustments appear almost as if they were specifically designed for Jesus Montero. Take a look at the modifications:

With the exception of the right center field measurement, Safeco's alterations draw it into eerily similar comparisons with U.S. Cellular Field, home of the Chicago White Sox, and Great American Ball Park, home of the Cincinnati Reds, two of the most homer-friendly ballparks in all of baseball. While that provides no promise of converting Safeco into a homer heaven -- personnel, climate, wind and playing surface also contribute -- there's a very real possibility that Safeco is the one of the two that will exhibit the larger statistical shift.

Returning to Montero, he has flashed outstanding power to left-center, center and right-center fields during his brief career, and among Mariners players, his 100 balls in play to left-center field led the team in 2012. Considering his modest 9.9 home run/fly ball percentage -- that number was only 7.8 at Safeco -- Montero might experience the greatest advantage as a result of the new dimensions. Certainly, however, Jason Bay, Kendrys Morales, Michael Morse, Justin Smoak and Casper Wells should also benefit. Again, we might be talking only 1-3 homers apiece.

Safeco's smaller dimensions might have a more adverse impact upon pitching than Petco's for another key reason: The Mariners are the one team of the two forced to face designated hitters rather than pitchers most nights -- meaning a ninth batter with legitimate ability to clear those closer fences. Perhaps this was one reason the team was willing to trade Jason Vargas; his 44.6 percent fly-ball rate the past three seasons combined would've put him at risk for increased ERA/WHIP. Instead, starter hopefuls Blake Beavan (45.6 percent fly-ball rate in 2012) and Hector Noesi (46.8 percent) will be the ones at greater risk for regression.

Safeco's visitors might also suffer, especially with the team adding Raul Ibanez, Morales and Morse this winter. Consider that visiting pitchers managed a 3.06 ERA, 1.16 WHIP, 55 quality starts and 27 saves in 81 games last season, numbers that made it the most favorable pitching venue. Tread much more carefully with your visiting starters, especially the fly-ballers: Vargas, Derek Holland and Tommy Milone, to name three, face a greater challenge in Safeco assignments.

Park effects for all 30 venues

Since we're on the topic of ballpark effects, why not re-examine the leanings of all 30 current venues? The charts below, as in the ones above, break down ballpark statistics into three categories -- BABIP, home run/fly ball percentage and isolated power, as well as by direction, left field, center field and right field.

Ballpark effects overall can also be seen on our Park Factors page, which breaks down the numbers in six categories -- runs scored, home runs, hits, doubles, triples and walks -- by season.

Left field

Ballpark measurements are in the four columns to the right: "dist." is the distance to the outfield fence, "hgt." the height of that fence. Left field measurements are from home plate to foul pole.

* 2012 statistics; outfield dimensions changed between the 2011-12 seasons. + 2012 statistics; opened in 2012.

The Fenway Park numbers are the most curious of the bunch, albeit unsurprising. As the Green Monster stands closer to home plate than any other left-field fence, and at a major league-high 37 feet, an increased number of doubles and triples will naturally inflate BABIP and isolated power to that part of the park. This is the reason fantasy owners might find offseason acquisitions Jonny Gomes and Mike Napoli, and to a lesser extent David Ross, particularly attractive; all three players managed better than a 40 percent fly-ball rate in 2012.

Minute Maid Park is the other venue that warrants attention: For most of its first decade of existence it had a hitter-friendly reputation, but as the Houston Astros' roster declined in talent in the past several years, it became more apparent that it was a good park for right-handed power … but neutral to pitching-friendly everywhere else. This is good news for winter acquisition Chris Carter, who has hit 15 of his 19 career home runs to left field.

Center field

Ballpark measurements are in the four columns to the right: "dist." is the distance to the outfield fence, "hgt." the height of that fence.

* 2012 statistics; outfield dimensions changed between the 2011-12 seasons. + 2012 statistics; opened in 2012.

Here is where Marlins Park, which opened in 2012, shows its true pitching-friendly leaning. Thanks to Giancarlo Stanton's immense raw power -- he clubbed 16 of the team's 55 homers at home and 11 of their 37 to left and left-center field there -- the venue's left-field statistics looked somewhat favorable but their stats to center and right field ranked among the game's worst. Only three ballparks have a deeper measurement to straightaway center field and two have a higher fence there; this might be a ballpark in need of a future Petco/Safeco adjustment of its own.

Take note of those higher BABIPs, which correlate with the teams with the deepest center field measurements. The larger the outfield territory, especially from power alley to power alley, the greater the probability of doubles and triples dunking in; that's why Coors Field has the highest BABIP to center field (.334) and fifth-largest measurement to that spot (415).

Right field

Ballpark measurements are in the four columns to the right: "dist." is the distance to the outfield fence, "hgt." the height of that fence. Right field measurements are from home plate to foul pole.

* 2012 statistics; outfield dimensions changed between the 2011-12 seasons. + 2012 statistics; opened in 2012.

The first thing you'll notice about right-field statistics is how much lower they are, on average, than those in left. There's a simple explanation: There are more right-handed batters in baseball -- 56 percent of the total plate appearances in 2012 were accrued by righties -- whose numbers on batted balls to right field will understandably lower those averages. Consider: Left-handed hitters had a 30.6 home run/fly ball percentage to right field last season, while right-handed hitters had a 28.5 mark to left. But righties had a 3.5 percentage to right field and lefties a 2.8 mark to left -- and the righties' sample was 2,871 plate appearances larger than the lefties' when going to the opposite field.

In other words, directional ballpark numbers shouldn't be compared to one another; they should be compared to their own league-average split.

Yankee Stadium, predictably, has an absurd power leaning to right field, but it's the extent to which that's true that might surprise you. There were 146 home runs hit to right in 81 games there in 2012 -- 98 by the New York Yankees, 48 their opponents -- which is good news for offseason acquisition Travis Hafner and also a plus for 2012 midseason pickup Ichiro Suzuki.

Look at the differential between Rangers Ballpark and Angel Stadium, however, most relevant pertaining to Josh Hamilton, who moved from the Texas Rangers to the Los Angeles Angels during the winter. Granted, analysis by Home Run Tracker founder Greg Rybarczyk showed that all but one of Hamilton's 2012 homers at Rangers Ballpark would've gone out of Angel Stadium, but who's to say that Hamilton will hit his fly balls to those same, precise spots in 2013? Climate differences could have contributed to those wide statistical splits between venues, and it's a primary reason Hamilton might lose a couple of the career-high 43 homers he hit last season as a result of the move.

In summary, remember personnel, as well as the fact that ballpark factors usually mean more like 1-3 home runs than 10-plus per player. You need the right players in order to exploit a venue's measurements, and you should never make rash decisions simply as a result of ballpark effects -- consider them more "tiebreaker" factors than primary decision-makers.

But as we tend to learn new things about each ballpark every year, perhaps we'll see, a year from now, whether things really changed that much in San Diego or Seattle.