On a four hour train ride from New York City back home to D.C. I had following a business trip this week, I listened to a lot of sports talk radio. At one point, on a show which I unfortunately do not know the name of, one of the hosts was previewing the N.L. East and pointed out that Gio Gonzalez has a career 4.32 ERA outside of the Oakland Coliseum, and wondered out loud why no one was talking about this.
While that number at first does jump out at you as troublesome, indicating that the Nats new hurler was a product of his park and not his talent, a deeper look at the numbers shows it really isn't that bad at all.
As we all know, Gonzalez is just 26-years-old and he has really blossomed in the last two seasons. For example, in 2008 as a rookie he posted a 7.68 ERA, and in 2009 in his first real full season as a starter he posted a 5.75 ERA overall. In 2010 and 2011 however, he won at least 15 games in each season and posted an ERA below 3.23, making him one of the stronger starters in the American League.
Given that, if you are looking at his career splits in ERA, you are taking into account his first two poor seasons. For example, in 2008 he had an astronomical away ERA of 7.99 and in 2009 he had a mark of 4.65. As you can see from his overall ERA above, these high numbers weren't a result of his inability to pitch outside of Oakland, but rather just his inability to get hitters out effectively at the Major League Level at that point in his career.
Striking those two years from his record, Gonzalez has a career 3.79 ERA on the road, which is a much less scary number. You can also point to the fact that each year his road ERA has gotten better, as you can see below:
2008: 7.99 ERA away from The Coliseum
2009: 4.59 ERA away from The Coliseum
2010: 3.92 ERA away from The Coliseum
2011: 3.62 ERA away from The Coliseum
That's good progression for a young pitcher. Of course, while his road ERA has gotten better some might argue that there is still a major split between his home and road ERA in general, which could make the argument that outside of the spacious stadium in Oakland he is just a mediocre pitcher. While that argument may have some validity, as there is a major split there, I think it's a reach to make that judgement. I would say it's much more likely that the majority of the game’s pitchers simply pitch better at their home park.
To prove this point, take a look at the home and away splits from last year's MLB ERA leaders:
Clayton Kershaw - Home ERA: 1.69, Away ERA: 2.87
Justin Verlander - Home ERA: 2.37, Away ERA: 2.43
Ryan Vogelson - Home ERA: 2.15, Away ERA: 3.57
Roy Halladay - Home ERA: 2.48, Away ERA: 2.33
Cliff Lee - Home ERA: 1.94, Away ERA: 3.03
James Shields - Home ERA: 2.36 ERA, Away ERA: 3.35
Jered Weaver - Home ERA: 1.84, Away ERA: 2.93
My best guess is that in 2012 we will see a strong home/away split again for Gio Gonzalez, as we saw for most of the pitchers above...but it will not be because Nationals Park is a pitchers haven, but because it is just significantly easier for a pitcher to pitch at home. I think a more pressing concern than Gio learning how to pitch outside of the Coliseum, is him learning how to pitch in a new league, with a new catcher, and new opposing hitters.