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Hiroki Kuroda used to pitch in the National League West, but now he has to pitch in the American League East

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Mood Music - Stranglehold by Ted Nugent

The concept that NL teams tend to favor slick fielding middle infielders and look for bigger bats in the outfield is supported, but there doesn't seem to be much else in terms of a pattern. The average NL position player provided a very comparable amount of production to the average AL position player. However, because of flimsy rationalizations about strategy, pitchers batting leads to an entirely different run environment.

In particular, the NL West has the reputation of being dominated by the pitchers, with strong starting rotations throttling weak offenses in giant ballparks. Conversely, the AL East is home to some high powered offenses and Yankee Stadium is a well known launching pad. To what extent is this true? Can the differences between the leagues be better articulated? How can we expect Hiroki Kuroda, who has pitched exclusively for the Dodgers, to translate to the Yankees? I will give satisfactory answers to none of these questions.

But, I do have some interesting things to share. Ballparks first:

To get an idea of the relative ballpark differences, I used ESPN's park factors to make a weighted average.* Then, I counted how many games were pitched in a hitter's park (parks 1-15 in friendliness to hitters) and how many games were pitched in a pitcher's park (parks 16-30 in friendliness to hitters).

A rating higher than one implies that hitting is being aided by the ballpark; a rating lower than one implies that pitching is being aided by the ballpark.

*Weighted average methodology example: CC Sabathia made sixteen starts at Yankee Stadium, which had a factor of 1.131, three starts at Fenway Park (1.173), etc. The weighted average is found by multiplying the number of starts at each stadium with the corresponding factor (16*1.131, 3*1.173, etc.), adding them all up, and dividing by the total number of starts (33).

I included everyone on the Yankees staff to make the point that pitchers on a certain team or in a certain division do not necessarily get the same number of starts in each ballpark. The NL West is a lower run environment, but if the schedule lines up in a way that you have to make three starts in Coors field, that makes a big difference. Ditto AL East in the very offense unfriendly Tropicana Field. There is a luck of the draw aspect to matchups, but all of the Yankees starters are clustered in an area very different than what Kuroda pitched in last year.

Coming from the ballparks that he pitched in last season to the ballparks that he will pitch in next season, we would expect the average pitcher's ERA to increase by around 10%. However, Hiroki Kuroda is Hiroki Kuroda and not the average pitcher, so to get a more detailed idea of what to expect, we must look further.

The average lineup faced by CC Sabathia in 2011 scored 733 runs (offenses in this range are the Blue Jays, Reds, Rockies, and Diamondbacks), whereas the average lineup faced by Kuroda in 2011 scored 662 runs (offenses in this range are the Angels, Cubs, and White Sox). But, while the run environment is lower, the NL West has not been beaten up by the American League. The difference in the overall quality of play is probably less than you've been led to believe.

In 2011, the NL West was 40-38 in interleague play (114-117 over the past three seasons). While the AL East was better (50-40 in 2011, 147-123 over the past three seasons), the NL West, and by extension, their pitchers, are not getting rolled every time that they play an American League team.

Hiroki Kuroda against the American League: 68.2 IP - 4.33 ERA - 1.15 WHIP - 7.2 K/9
Hiroki Kuroda against teams with a winning percentage above .500: 329.2 IP - 3.28 ERA - 1.14 WHIP - 7.0 K/9

I haven't heard it cited* as a red flag against Kuroda, but his ERA against the American League is almost a full run higher than his career rate (3.45). But, with pretty similar peripherals, a small sample size, and a career of pitching well against good teams, I wouldn't get worked up about it. I wouldn't entirely dismiss it, but his limited amount of exposure to the American League has not been a disaster.

*Because everyone thinks Michael Pineda is more fun to talk about than Hiroki Kuroda.

The real question is how Kuroda's pitching style will play in smaller ballparks against nine American League hitters. As the five teams in the AL placed first (Yankees - he doesn't have to pitch against them!), third (Red Sox), fourth (Orioles) and eighth (Rays) in home runs hit in 2011, a lot of his success or failure may boil down to his ability to keep the ball in the park.

While this has historically been a strength of his, 2011 saw him set career highs in HR/9 and HR/FB to go along with a career low in GB%. As a pitcher who has always relied on control and keeping the ball in the infield, this will become especially important with a move to the short porch of Yankee Stadium.

Looking at the true landing spots of the twenty-four home runs given up by Kuroda in 2011, the majority of them would be home runs in Yankee Stadium. The encouraging news, however, is that fourteen of those were hit to left field, where he will now find ample space for Brett Gardner to chase down his mistakes.

So, with those somewhat intuitive reasons to expect a move to the AL East to affect his performance, here are a few reasons to be excited:

Kuroda has posted an ERA, FIP, and xFIP below 4.00 every year of his career.
Kuroda has thrown 398.1 innings over 63 starts the past two seasons.
Kuroda's career high WHIP is 1.22 and his career high BB/9 is 2.20.
Conventional wisdom says that pitchers get an advantage by switching leagues because they're less exposed to the other league's hitters. I'd probably object to this until someone showed me proof (a post for another day), but it could be true.

Baseball will be played again soon.