What can we expect from Kang Jung-ho?

By Byung Joon Yoon

What can we expect from Kang Jung-ho, the newest recruit of the Pittsburgh Pirates hailing from Korea? The Pirates spent 16 million dollars on posting for Kang over a guaranteed 4-year contract. Then the question becomes, can Kang live up to the expectation of the team and prove worthy of his contract? Let’s find out. From my last article, we expected slash line of .242/.303/.346/.649. We will try and calculate Wins Above Replacement, and assuming $5 million per each WAR, try to determine if he is expected to pay for himself. We will also try to draw some conclusions, stemming from his WAR calculation and his situation with the Pirates. For ease of calculation, we’ll assume that he will get full-time play at shortstop, while in fact it is pretty likely that he will be used as utility man; so there is a possibility of over-calculation.


In order to get WAR, we need wRAA values. However, getting that value from scratch is really complicated, including over 10 variables that we don't have. So, I used simplified version(courtesy of Kincaid from http://www.3-dbaseball.net/2009/11/converting-obpslg-to-woba.html) which indicates the following:

x = .56*OBP + .31*SLG

wOBA = -.53x^2 + 1.35x - .045

The coefficients are generated by using regression to build a statistical model on OBP, SLG and wOBA, which is described in detail in the Kincaid’s blog post, as cited above. And substituting Kang’s expected slash line into the equation gives a 0.289 wOBA. Using fangraph league average in 2010, and assuming PA around 650(full time), all other variables(running, fielding, etc) to 0 to calculate wRAA:

wRAA = ( (wOBA - .294) /1.25) * (AB + BB + HBP + SF + SH) +Positional adjustment(7)

This gives a wRAA = 4.4, using Kang instead of replacement-level shortstop produces 4.4 more run a year. Assuming 10 runs = 1 WAR(as is norm), it translates to 0.44 WAR; if he were to continue performing like that for four years, it will add up to 1.76 WAR, and pirates will not only not exercise his option ($5.5 million), but also will regret their initial investment in Kang, as they expected a WAR around 3.2 over 4 years. Considering that this has a large risk of over-estimation, Kang really has to perform better than this; if he hitting statistics matches the calculations above, it is not likely that he will be full-time SS, rather he will be used as a role player or utility player, which will drive down his WAR even lower (Kang is a replacement level player at 3B and 2B) . Most similar player is Xander Bogarts, who had 0.2 WAR in 2014 (.240/.297/.362), but Kang is 5 years older than him, and costs at least 5 times more than he does.

It is obvious that on the surface, that the Pirates overpaid for Kang. Moreover, the Pirates infield has a good substitute at SS, in Jody Mercer (WAR 2.8). But considering 2B Neil Walker (2014 WAR 3.6) might leave and 3B Pedro Alvarez (2013 WAR 3.7, 2014 WAR 0.8) might move to 1B (25 errors in 99 3B appearances in 2014), and 3B Josh Harrison having a break-out year just last year (he was pretty bad both in defense and offense at 3B before last year), it is clear that Pirates infield is not as strong as it seems, so Kang will be a good player to have, albeit he is a bit expensive to use as a utility man. The Pirates organization is obviously hoping that he will improve and hit better than expected slash line of .242/.303/.346/.649, but even if he doesn't, he will be a good short-gap before Pirates can find somebody to play short stop at the major league level. All in all, he is adequate acquisition, able to provide some utility use as he is, but he is quite expensive bit expensive, but if he improves, the investment in Kang might be worth it.

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