Arguably the most far-reaching impact of sabermetrics is in the use of park factors to put player performance in context. Throughout baseball history, players, fans and executives knew that certain parks changed the game and the statistics, from the Polo Grounds' horseshoe outfield to Yankee Stadium's short porch to the vast expanses of Sportsman's Park in St. Louis. It was statheads who started hanging numbers on those elements, though, enabling us to evaluate players more accurately.
One of the most important things we learned was that ballpark factors bounce around from year to year, owing to the half-season nature of the data (81 games a year in any park) and the changing personnel who play through. Serious analysts have determined that you need three years to evaluate a park, and some use as many as five in setting their adjustments. All agree that using one-year park factors is a mistake -- too small a sample to rely upon.
Of course, perceptions can be hard to change, so when you think about Minute Maid Park in Houston, you think of it as a bandbox, because in 2000 it was the fifth-easiest park in which to hit a home run, and like playing on the moon after years of games in the Astrodome. In 2001, though, it played as both the hardest park for homers and run-scoring in all of baseball. Since then, it has generally rated as a slight hitters' park, and its three-year factors reflect that. You see this kind of jumping around all over single-season ratings; Cleveland's Progressive Field was the best hitters' park in the game based on 2001 data, but it was the second-best pitchers' park in baseball based on 2009's. Some parks routinely occupy one end of the spectrum -- Petco Park in San Diego has always been great for hurlers -- but for the most part, one year of data is unreliable.
Think about the Mets' new home, Citi Field. All of the coverage in 2009 focused on how tough it was on the Mets' hitters, what with the deep outfield and high walls. And yes, it did play as a pitchers' park, 6 percent more difficult for run scoring. But home runs were, in fact, slightly easier to come by at Citi Field than in other parks, by about 4 percent. The Mets' injury problems last season, which would have made them a lousy homer team in Williamsport, were why they didn't hit for power at home. They didn't hit for power anywhere, because they didn't have the personnel for it. Citi Field was a scapegoat.
So far in 2010, Citi Field has been tough on hitters and home runs, but if one season is too small a sample, one quarter of one season is useless. Certainly the Mets are bucking the trend, with a higher slugging average and isolated power on the road than at home, same as they had in 2009. We'll need three years to sort out what kind of park Citi Field will be, and reaching conclusions before that time -- and certainly, making personnel changes or alterations to the park before that time -- is a mistake.
Mets fans obsessed over the park a year ago because of how poorly their boys played in it, with much of the focus on David Wright's power outage. Wright, however, didn't hit for power at home or on the road, having a strange season in which he increased his strikeout rate without getting any power from that increase. The dip in his home run total was a fluke, the product of a 6.9 percent HR/FB rate that wasn't tied to his home park. (That number is back to 17 percent this year, just about matching his 2007-08 rates.) Much was made of his poor performance and high strikeout rate after an Aug. 15 beaning, but even before that Wright was striking out more than he ever had.
Wright has continued that trend in 2010, and in fact, appears to have permanently changed his approach at the plate. Over two years, Wright's strikeout rate has doubled with only a small uptick in his walk rate. He seems to be consciously trying to hit the ball out of the park now, trading line drives for fly balls, swinging and missing more both at pitches in and out of the zone. The change hasn't been a positive one; Wright is still a productive player, but at a level below his 2005-2008 peak, as the lower batting average and OBP hasn't been matched by a rise in walks or isolated power.
No player doubles his strikeout rate over two years without it being a change in approach or a physical factor. Wright, it seems, reacted to the Mets' loss of power last season by taking it upon himself to hit like a cleanup guy, and in doing so, has made himself worse. The Mets don't need Wright to hit home runs; they need him to be the best player he can be, and that means getting back to what made him a star through his peak, being selective at the plate and hitting line drives into the gaps.
New Met Jason Bay has also been the subject of speculation that Citi Field is hammering his power numbers, but again, the data doesn't support the theory. He's hitting more or less the same this year as he did a year ago, but his fly balls aren't leaving the yard: just 5.2 percent HR/FB. That number is 0 percent on the road, so it's not a Citi Field thing. Bay, in fact, is raking at home (.347/.442/.584) and doing nothing away from it (.230/.301/.284). He may have just three longballs, but everything else is working. He's hitting the same number of fly balls that he always has, roughly the same walk and strikeout rates, a bit down in both cases. He's chasing a bit more and falling behind a bit more than usual. Really, the only unusual thing about Bay is his home run total, and, like Wright's a year ago, it's a fluke that doesn't say anything about him as a player.
The middle of the Mets' lineup isn't their problem. David Wright and Jason Bay are productive hitters who get on base and hit for power, perfectly capable of being the 3-4 on a championship team. The Mets' problems are elsewhere, and obsessing over the numbers of their very best players distracts from addressing the real problems with the offense, such as the catcher and right fielder with the sub-.300 OBPs, neither of which is a new-park fluke. Mets fans need to stop blaming their best players and save their ire for their worst.