Factors such as altitude, humidity and wind affect how ballparks at all levels play for hitters and for pitchers. High altitude, low humidity and a steady jet stream are the perfect recipe for hits, homers and runs. No parks exemplify this quite like High Desert and Lancaster, the high Class A California League's two most hitter-friendly locales.
A park at or near sea level with still, humid air will almost always favor pitchers. Examples include Savannah of the low Class A South Atlantic League and Wilmington of the high Class A Carolina League. For league-by-league ballpark characteristics for the full-season minors, check out the recently published feature Minor League Parks Drive Performance. Go ahead and click—it's free.
A ballpark's features really come into focus, though, when a player in a hitter- or pitcher-friendly park ventures onto the road. Take High Desert as an example. In the three seasons from 2010 to '12, the Mavericks and their opponents accounted for an average of 14.65 runs per game in High Desert, compared with 10.07 per game away from High Desert. That ratio works out 1.455, which implies that playing in Mavericks Stadium during the past three seasons increased the frequency of runs by about 45.5 percent in a typical game (compared to that same rate in road parks the Mavericks visited).
Given that home-road comparison for Mavericks games, we can arrive at a simple park factor to apply to individual High Desert players. To get there, we take the 1.455 ratio and reduce its impact by half—in this case, 1.228—to reflect the fact that a team's players spend only half their games at home.
Here are the highest and lowest three-year park factors for runs scored for the 10 full-season minor leagues:
|THREE-YEAR PARK FACTORS FOR RUNS SCORED|
|California||High Desert||SEA||1.228||Inland Empire||LAA||.894|
|Florida State||Bradenton||PIT||1.107||Brevard County||MIL||.908|
* Scranton/W-B had lowest PF for 2010-11 (.922) but had no home park in 2012
** Birmingham moves into Regions Field in 2013; next lowest was Mississippi (.937)
Albuquerque, High Desert, Asheville and Lancaster rank one, two, three and four in the full-season minors for runs scored park factor since 2010. Columbus ranks sixth and Northwest Arkansas eighth. Due to the offensive nature of the western reaches of the Pacific Coast League, many of that league's pitcher's parks—yes, they exist—rate as having extremely low park factors. Examples include Sacramento (.874; lowest in minors) and Tacoma (.885; third lowest).
Practical application: Albuquerque righthander John Ely won the PCL's pitching triple crown last season, going 14-7, 3.20 with 165 strikeouts in 168 2/3 innings. That feat becomes even more impressive when placed in the context of Isotopes Park, which has enhanced run scoring per game by roughly 23 percent since 2010. As it turned out, Ely made 14 starts at home and 13 on the road, making him a perfect candidate for a park-factor adjustment. His ERA may have been 3.20, but Ely actually gave up 3.63 runs per nine innings. Taking that rate and dividing by the 1.229 park factor gives us an adjusted runs-allowed rate of 2.95.
Now let's examine the three-year park factors for home runs, checking the extremes in each league:
|THREE-YEAR PARK FACTORS FOR HOME RUNS|
|Midwest||Lake County||CLE||1.248||West Michigan||DET||.871|
* Pensacola had highest HR factor (1.345) in 2012, their first year in league
** Birmingham moves into Regions Field in 2013; next lowest was Mississippi (.813)
Low Class A Greensboro players have received the largest home run boost in the full-season minors since 2010, with NewBridge Bank Park featuring 43 percent more home runs than in Grasshoppers road games. Next on the list are High Desert, Columbus, Frederick, Asheville (1.306) and Albuquerque.
Practical application: One size fits all is not a label that seems to fit home run park factors at the minor league level. For example, the Marlins have had a number of fine hitting prospects pass through Greensboro in recent years, but none has derived a great advantage from playing half his games at NewBridge Bank Park and its 1.430 factor for home runs. Consider: Giancarlo Stanton hit 21 of his 39 home runs there in 2008, while 2011 Grasshoppers Marcell Ozuna (13 of 23 at home) and Christian Yelich (eight of 15) both hit for equal power home and away. Yet, the Grasshoppers as a team hit 43 percent more homers at home than on the road, suggesting that marginal players receive the biggest boost, and that top prospects like Stanton, Ozuna and Yelich receive less benefit.
One telling example might be Indians first baseman Matt LaPorta, who hit 14 of 19 homers at home for Columbus last season, and all six of his Triple-A homers during 2010-11 also were hit at home (in a limited sample of 20 total games). Taking just his 2012 output: If we adjust LaPorta's 14 home runs by the Columbus home run factor of 1.350 we arrive at 10 home runs.