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Bartolo Colon, a misleading ERA, and big ballparks

Looking at Colon's ERA, you would think he is having a bad season. But we know better than that ... especially in the ballpark where he pitches his home games.

Jim McIsaac

Bartolo Colon likes big ballparks. Or he should. You will find out why in a minute. And why his ERA this season is a poor indicator of his actual performance.

Colon is coming off three seasons - two with Oakland and one with the Yankees - in which he saw his performance steadily improve. His ERA dropped from 4.00 with the Yanks, to 3.43 the following season in Oakland, and ultimately to 2.65 in his spectacular campaign last year. Coming to the Mets as a forty, turning 41-year-old pitcher, it seemed like the right fit. If there has been one thing to plague Colon throughout his career, it has been his propensity to give up home runs. Citi Field is where home runs go to die.

So far, pitching for the Mets, a casual observer could look at Colon's ERA, inflated to 4.73, and think the right-hander is off to a poor start. Of course, a casual observer wouldn't know to look at his FIP, which is at 3.66, or right in between his stellar 2012 (3.82) and 2013 (3.23) seasons.

We could look at Colon's ERA, judge that he is pitching poorly, and move on. Or, we can consider the factors that are better predictors of future performance, like FIP, and realize that he is doing everything that made him very good the past two seasons in Oakland. We are then more confident in expecting performances like he had over his last two starts - 15.1 innings, 10 hits, 14 strikeouts, 2 walks, and 2 earned runs.

What is FIP and why should I care?

Fielding independent pitching (FIP) measures what a pitcher's ERA should look like considering the factors directly within their control. In other words, by looking at walks, hit batters, strikeouts, and home runs allowed, we can get a better idea of how a pitcher is performing than simply relying on their ERA, which is victim to many factors outside of their control, as in luck, measured by batting average on balls in play. Colon has a BABIP of .322 this season, up from .294 last season. This means more balls are falling for hits, which could be a result of poor defense - the Mets ultimate zone rating ranks 17th this year - or simply too many well-placed balls finding open grass.

Why is Colon's ERA so high considering his FIP?

While Colon's FIP is lower than his ERA, that doesn't absolve him from the runs that he has allowed. It tells us that he has had some bad luck. Knowing his strikeout rate is high and walk rate low, it also tells us that he is giving up far too many home runs. Which brings us back to our point about big big ballparks, and why, as the season continues, we can expect to see Colon's numbers improve. But we will get to that in a bit. I promise, stay with me...

HR/FB rate is often viewed as a luck statistic. Meaning, analysts like to look at a pitcher's HR/FB rate, and if it is too high, they can conclude that eventually it will drop. The exception is when you get a pitcher like Colon, who over a long career has seen his rate balloon to 14 or 15% in given seasons. Then, all of a sudden, during the past two seasons, his rate dropped precipitously. There is a reason for that.

Why does Colon like big ballparks?

Perhaps Bartolo Colon is getting wiser with age. After pitching for the Yankees, where he was demoted to the bullpen, he signed with Oakland. The spacious outfield at the Oakland Coliseum, now missing a few letters, so referred to as Coliseum, offered a stark contrast to the short right field porch in the Bronx. There was a lot more outfield to hold fly balls in the park. A perfect setting for an ageing starter looking to rejuvenate his career.

Bartolo Colon gives up a lot of fly balls - nearly 12% more than league average over the past three seasons - which is why it is important to look at his HR/FB rate in relation to his ERA. While a pitcher doesn't have a lot of control on how many fly balls turn into home runs, there are two direct ways they can impact the number: one, they can generate more ground balls, or two, move to a more spacious park where fly balls turn into outs.

Colon has had moderate success improving his ground ball rate in the middle of his career, but saw the number of ground balls decline in recent seasons. He continued to give up those fly balls, and hoped his new location would help keep them from turning into round-trippers.

Sure enough, pitching in Oakland, his home run to fly ball ratio steadily dropped from 11.4% while pitching at Yankee Stadium to rates in Oakland of 9.1% and 6.0%. In fact, more precisely, his rate was a minuscule 3.8%, pitching in Coliseum in 2013.

Thinking back to FIP, which measures things directly in a pitcher's control, home runs are included in the calculation. If we believe that home runs fluctuate based on the size of the ballpark, we can use xFIP instead, which adjusts for league average HR/FB rates. This isn't perfect, since HR/FB rates aren't directly a result of ballpark size, but it helps in our analysis. If xFIP is better than FIP, it suggests the pitcher plays in a ballpark that allows less than average long ball rates. Colon's xFIP (4.17) was worse than his FIP (3.82) when he played most of his games at Yankee Stadium. Pitching in Oakland, and now Queens, his xFIP has improved over his FIP, or simply, his HR/FB rate could have declined due to the home ballpark.

Although Colon found success in Oakland, he decided to sign a two-year contract with the Mets this past offseason. A smart move considering Citi Field is another park where power is thwarted.

If he's pitching in Citi Field, why is Colon's home run rate back up this season?

This is where sample sizes are extremely important to pay attention to as an analyst. Looking at Colon's HR/FB rate in 2014, we see that it has ballooned back over 10%, and could easily assume that he is struggling again. One bad start is carrying that entire number. If we remove the four dingers he gave up in a five inning start in Anaheim, Colon's HR/FB rate looks much more respectable, it would be 5.8%. That means in over 92% of the innings he has pitched this year, he has done an excellent job in keeping the ball in the ballpark.

As expected, Colon is allowing more home runs on the road than at home this season. His HR/FB rate at Citi Field is 6.9%, compared to 12.3% on the road. Of the nine home runs allowed by Colon, only two have come at Citi Field. Ironically, one was hit by a pitcher, Gio Gonzalez. Overall, pitching in Queens has been quite welcoming for the portly right-hander. His ERA at home is 2.30, compared to 6.51 in other parks. FIP reminds us that the gap is largely due to the amount of home runs he has allowed on the road, seven already. Of course, four of those are in one start, so even on the road there are signs that he is pitching closer to his 2012 and 2013 numbers than his ERA suggests.

What does this all mean?

Colon is doing two things exceptionally well this season. He is striking out a lot of guys, at his highest rate since 2011. And he is not walking anybody. His K-BB% of 16.2% is the largest split of his career. The only thing keeping him from exceptional numbers overall has been his home run rate. He has allowed nine long balls over 64.2 innings; he allowed 14 all of last season in 190.1 innings. This explains why his FIP is lower than his ERA. Two of the main factors to calculate FIP are strong. For those seeing alphabet soup, reading F-I-P, all this means is that he is likely to pitch better than his ERA reflects.

We know that pitchers don't have a ton of control over how often fly balls fall over the fence. The best they can do is try to produce more ground balls, or pitch in a ballpark that turns fly balls into outs. Pitching in Citi Field, like he benefited from in Oakland, should help keep Colon's HR/FB rate down. And it has. When we look beyond Colon's ERA, we learn something. We see that he has actually pitched pretty good. So don't let that 4.73 ERA fool you.

. . .

All statistics courtesy of FanGraphs.

Jeffrey Bellone is a writer and editor at Beyond The Box Score and can also be found writing about the Mets at Amazin' Avenue and Mets Merized Online. He writes about New York sports at Over the Whitestone. You can follow and interact with him on Twitter @OverWhitestone.