Going into this season, it was obvious that Prince Fielder was leaving a park that was friendly to his lefty power and going to one that was less cozy. The difficulty in using that one fact to predict Fielder’s 2012 power was that he’d play half his games in other parks. So Chad Young and I tried to correctly weight the lefty home run power factors for each of the stadiums he’d see. Our answer was that he’d see a 6.7% reduction in home run production on the road. Combined with a 30% drop at home (118-88), he could expect a 18.65% drop overall.

Edit: Nailed it!

If you use Fielder’s 38 home runs in 2011 as his true talent production, then an 18.65% reduction would have seen him hit 31 this season, not 30, so we were off. So his power kind of took a nose dive, and you can see it easily in his isolated slugging percentage, which fell from .267 in 2011 to .215 in 2012.

But if you look at his career, he’s oscillated all the way from a peak of 50 home runs to a nadir of 28 (and a peak of a .330 ISO and a nadir of a .213 ISO)… and those were in consecutive seasons. The 28 year-old is still in his peak age range, and his best home run season came in his second season, so let’s try something a little unconventional. Prince Fielder has averaged… 38 homers a year in his career. Hmmm. Well, weighting systems usually only look back about three years. Prince Fielder has averaged… 39 homers a year over the last three years going into this season.

No matter what, Prince Fielder saw a huge reduction in home run power. Is there more going on, though? There was some evidence that power peaks earlier, could he past his power peak and in a stadium that only exacerbated that situation?

Here’s (perhaps) an amazing thing: Fielder hit the ball just as hard in 2012 as he did in 2011. In fact, he’s hit the ball just about as hard on fly balls and home runs his entire career! Take a look:

That’s good power, too. Last year’s 299.7 feet on home runs and fly balls came in 18th in the league among players with 70+ home runs and fly balls, right behind Miguel Cabrera and Carlos Quentin, and above Ike Davis and Giancarlo Stanton. And it’s been steady even while his home run (and general power) production has oscillated.

Maybe there is something going on in his batted ball mix. If he’s an opposite-field guy in a park with a long left-center power alley, his home runs could have been dampened even as his batted ball distance stayed the same. Over his career, Prince Fielder is more of a pull guy — his ISO to the pull fields is an enticing .420, while to center (.254) and left (.255) he’s merely strong. This year, his power to center disappeared (.136 ISO). That’s the worst center-field power he’s ever shown. Only once did he even show a sub-.200 ISO to any field, and that was to the opposite field in 2008.

Center field has usually been good to Fielder. Center field in Milwaukee is 400 feet out. Center field in Detroit is 420 feet out. Oof. Might the extra five home runs have gone there? Fielder hit five home runs, one double and 32 singles to in 82 plate appearances that ended with a ball going to center field in Comerica this season. That’s a .196 ISO and not great, but also better than his road center field ISO.

Here’s another problem: Prince Fielder hit 18 home runs at home in 2012, and only 12 on the road. His home ISO was 48 points higher than his road ISO (.192). The Cell, Progressive Field, Target Field — they’re all smaller in center field than Comerica, and yet Fielder didn’t muscle the ball out of those parks any more than he did at home. In fact, despite his more difficult home park, Fielder continued his long-held belief that home cooking is the best cooking:

There isn’t going to be a pretty bow on this. Prince Fielder sometimes hits closer to 30 home runs, and sometimes he hits closer to 40. We can’t blame his home park for all of his light power production in 2012. What we can do is pay for the worst-case scenario (.200-.210 ISO, 30+ home runs, plenty of runs and RBI) and reap the benefits if the more powerful version shows up.