Revisiting the riddle of Citi Field

Let's take another stab at figuring out what makes Citi Field unique and how Sandy Alderson plans to construct the Mets going foward.

If the beginning of the season is a time for predictions, then the end of the season is time for mea culpas. What good are predictions and theories if we don't go back and see how they did? And now that the Mets have decided to bring the fences in, it seemed like a good time to revisit a post I wrote before the start of the season.

You can read that post here, but the cliff notes version is this: Based on a data point from a Tony Blengino piece at Fangraphs and some circumstantialevidence, I posited that Citi Field might have a fly ball park effect that made fly balls more dangerous. That, or the Mets' bad outfield defense, was being continuously exposed, leading to poor home records for every team of the Alderson era. Given this information, wouldn't the signings of two former center fielders who hit fly balls make sense?

The Mets finished 40-41 at home this season, their best such record under Alderson. They also had their best season of outfield defense in the Citi Field era, at least according to Defensive Runs Saved.

But what about that whole dangerous fly ball factor? Yeah, so, uh—it turns out fly balls are not more dangerous at Citi Field. Blengino revealed as much himself a few weeks after dropping that original nugget. In a post about why we should start worrying about Curtis Granderson, he revealed that, based on his calculations, the fly ball park factor to right-center field in Citi Field ranks 17th in baseball and the right field fly ball factor ranks 27th. It seems unlikely there is anything going on in right and center field to make up for this and make Citi have an above average fly ball park factor.

Further debunking the dangerous fly ball theory, the Mets hit .129/.126/.355 on fly balls—in total at home and on the road—in 2014 versus a league average of .153/.149/.438. You will probably note that Mets had worse players than league average. That's true, but their .481 OPS on fly balls is good for third-worst mark in baseball. If there were a dangerous fly ball factor at Citi Field, my hunch is they would rank a bit higher than that.

So let's crumple up that theory, toss it in the trash, and set it on fire. As it smolders, let's ponder some of Citi's actual park factors and try to figure out how they can be applied to the 2015 Mets and beyond. Before we jump in, it's important to understand how park factors work. Here's a good layman's explanation. Here's something more in depth.

Now, here are the park factors by handedness for Citi since the fences were moved in before the 2012 season, where 100 is average and each tick above or below is a percentage point above or below average. All data via Baseball Prospectus:

This is probably not enough data to know exactly how the ballpark plays, but this is all we have—and all we will have thanks to the fences changing again—so let's roll with it. What stands out is that Citi Field is not a below average home run park. In fact, it's above average. How is this possible? Moving in the fences in left certainly made a big difference, but how is it not below average for lefties with that cavernous right-center field?

The answer, I think, lies in some of the other factors inherent to the park. Below is a table of the park factors for batted balls, in terms of frequency. Again, data is from Baseball Prospectus:

The most obvious standouts here are the fly ball and pop up factors. Something about Citi Field causes batters to get under the ball a bit. More fly balls, generally, means more home runs. There are any number of variables that could be creating this effect. The same factors that affect strikeout and walk park factors—batter's eye, lighting, weather, etc.—are likely to contribute to these batted ball effects. This factor appears to be one of the most consistent and quirkiest factors about Citi Field. If we take it as a given that fly balls are more frequent at Citi, and that fly balls, as a rule, are more dangerous than ground balls, what do we do with this information?

You would still want to emphasize outfield defense. More balls in play are going to the outfield so you want to ensure those fly balls become outs. The Mets had an expansive outfield these past few years with some estimating Citi had the third most outfield acreage in baseball. So if you have a big outfield with an above average number of balls potentially being hit there, you definitely need good defenders to cover that ground. The Royals and their large outfield coupled with good defense serve as an example.

You're also going to want to stock your team with fly ball hitters, and here is where moving the fence in comes into play. Playing half your games in a park where fly balls are more frequent gives you an advantage on your opponent. You can, in an ideal world, structure your lineup such that the majority of your hitters are of the fly ball variety. More fly balls, in theory, equals more extra base hits and home runs, especially if your fences are at a reasonable distance.

Likewise, it gives you the opportunity to fill your staff with pitchers who suppress home runs. That means not signing fly ball pitchers like Bartolo Colon and focusing more on ground ball pitchers who can limit fly balls. Pitchers like Zack Wheeler, who had a 54 percent ground ball rate in 2014 versus a league average of 44.8 percent. Matt Harvey, who in 2013 allowed home runs on just 4.7 percent of his fly balls allowed, less than half the league average. Jacob deGrom had a slightly above average ground ball rate this year and a well below average home run per fly ball rate. And out in Vegas, just 23.9 percent of Noah Syndergaard's balls in play were flies, where league average was 28.6 percent. Colon is a guy who could continue to get exploited in this park. In 2014 his fly ball rate at home was 40.1 percent, well above the league average of 34.4 percent. That might not be the best fit for a fly ball park that's having its fences moved in. It's part of the reason I expect him to be moved this offseason. That and his $11 million price tag.

Of course, the Mets need better players in general. Just because you can hit fly balls does not mean you will automatically hit for more power. Chris Young hit an extreme amount of fly balls this year, 52.5 percent of his balls in play, but produced just a .103/.100/.333 line on those balls thanks in no small part to an average fly ball distance of 273 feet, good for 191st in baseball. Young had also been a pop-up artist for most of his career, so bringing him into a park with an extreme pop-up factor probably didn't help. Similar to Young, Granderson hit a well above average number of fly balls but also averaged just 273 feet on his fly balls. You need to hit fly balls and you need to hit them far. There are things to be encouraged about. Lucas Duda is an extreme fly ball hitter (much more so than Ike Davis) and he finally broke out this year while averaging 298 feet per fly ball, good for 22nd in baseball. Wilmer Flores, Dilson Herrera (in a small sample), and Travis d'Arnaud all displayed above average fly ball rates this year.

I want to note that this is merely an attempt to understand the thinking of the organization and to try to put some context around some of the moves they make. The Mets need to acquire better players above all else. But they are still a small-mid market team in terms of payroll, and small-mid market teams need to squeeze the margins for every possible win. And regardless of their payroll, they need to be aware of the factors in their ballpark, as I'm sure most clubs are. Here's an interview with Bill Geivett, former vice president of major league operations with the Rockies, talking about how in Colorado they focused on bringing in ground ball pitchers and how they become even more extreme ground ball pitchers in Colorado. And, sure enough, although somewhat counter-intuitively, Colorado has one of the highest ground ball park factors in baseball. This gives some insight into how a front office thinks. Teams should play to their strengths, and a known variable for 81 of your games is certainly a strength. I think that's what you're seeing with the moving in of the fences and what you'll see throughout the offseason, as well.