Measurement of a baseball stadium's park factors is still far from perfect science. The vagaries of weather, changes in the ballpark's dimensions, and the ability to factor out differences in the players involved all make for inconclusive results. For years, Petco Park, located close to the Pacific Ocean in San Diego, has been considered one of the least friendly parks in the game for hitters. This may be related to Justin Upton's .790 OPS last year, a slight decline in his only season with the Padres. However, he still hit 26 home runs, 15 of which came at home.
The slight drop-off begs the question: how will Justin Upton's power play in Detroit?
Despite a stark contrast in reputation, Comerica Park and Petco Park have similar dimensions, especially in left field. Petco has a shorter porch down the left field line, but the slope back towards center field is a bit steeper, leaving him with shorter fences in left field (345 feet) and left-center (370 feet) than he tested in San Diego. That bodes well for the right-handed Upton, who pulls the overwhelming majority of his home runs. Here are his 2015 homers set into Comerica's dimensions.
The greatest difference between the two stadiums is clearly in center field. While Petco Park's center field fence stands just under 400 feet from home plate, Comerica's cavernous dimensions stretch to 420 feet in dead center. A glance at Upton's 2015 charts shows several home runs he hit last year that would not have gone out in Comerica. To his credit, all of them were measured at 399 feet or more, so they are leaving the park in all but a few stadiums around the league.
Where things get really interesting is in right field, where the reasonably shallow porch in right diverges from the "triples alley" in deep right-center field. In 2015, Upton hit a good many deep balls to straightaway right field, and several of those would likely have cleared the wall in Comerica. Upton carried quite a few balls to right field in the 340-360 foot range. It's quite possible we'll see Upton follow in the footsteps of Miguel Cabrera and J.D. Martinez, two of the most notorious right-handed hitters in the game in terms of smoking opposite field home runs.
The final question is whether Comerica is really a better hitter's park overall than Petco Park. Certainly, you would expect that gaining 600 feet of altitude from a seaside park would help Upton's power. The marine layer atmosphere can wreak havoc on power hitters playing on the west coast, especially during night games.
However, the difference might not be that big. Kevin Ruprecht of Beyond the Box Score posited that Petco Park is no longer a death trap for power hitters after the Padres moved their right field fences in prior to the 2013 season. The move had a larger impact for left-handed hitters, though.
Here's the big difference: in that 2010-2012 period, Petco saw only 30 percent of its home runs from lefty hitters. From 2013-2015, 45.6 percent of Petco's homers came from lefties. In contrast, 41.3 percent of all pitches in Petco in 2010-2012 were thrown to left-handed hitters. That increased to only 44.7 percent in 2013-2015, not enough to explain the increase in homers by lefties. The fence move here had its intended effect. Lefties can hit in Petco.
The change in home parks alone isn't going to lead to a 40 home run season for Upton. In fact, Comerica Park may swallow a few balls in center field that would leave most other stadiums.
Wherever he fits in the lineup, Upton should thrive as part of the most dangerous lineup of his career. Simply repeating his recent seasons would make him plenty valuable to the Tigers. He should produce plenty of offense, regardless of where he plays his home games, and maybe unleash the kind of monster season that his early promise led so many to expect.