Hiroyuki Nakajima is a much better baseball player than Tsuyoshi Nishioka. That's good news for the Oakland Athletics, who signed him to a two-year contract this week, and it's bad news for me, since I just got done writing thousands of words about how the Cardinals should sign Hiroyuki Nakajima. In any case: Here's one good reason to believe Hiroyuki Nakajima is a better player than Tsuyoshi Nishioka, who had a truly awful two-year stint with the Minnesota Twins before going back to Japan.
It's easy: Tsuyoshi Nishioka was not as good a hitter as Hiroyuki Nakajima, then or now, even though it looked like he was.
Nishioka did have one outstanding season to his name. In 2010, the year before he left for Minnesota, he hit .346/.423/.482 as a 25-year-old with the Chiba Lotte Marines. The seasons before it weren't as good, but he showed solid plate discipline and doubles power in each of them.
You'll hear this a lot: In his last two years, Hiroyuki Nakajima has hit .303/.367/.441. Why the last two years? Because in 2011, the year Nishioka spent in Minnesota, offense cratered in Japanese baseball, and it hasn't come back since. In 2010 Nakajima was nearly as good as Nishioka--he hit .314/.385/.511, his third season in a row within a few points either way of a .900 OPS. That year, as both of them vied for the title of best shortstop in the league, the Pacific League average line was .270/.336/.403.
In 2011, with Nishioka gone, it was .251/.308/.348. All those scary five-foot-nothing infielders who hit 30 home runs in Japan and then slapped the ball around in America began slapping the ball around in Japan, and aside from Wladimir Balantien and Nick Stavinoha (you can look it up) everybody stopped slugging .400. The league looked much the same in 2012.
Adjusted for context, then, with some very rough Google-Docs OPS+, here's what their last three years before leaving Japan look like.
Nakajima, then, is coming off a better season--adjusted for context--than Nishioka was. And you'd be hard-pressed to find a more consistent hitter in Japanese baseball, even as Japanese baseball itself has fundamentally changed; he's consistently been among Japan's best hitters since 2008, his breakout year.
That might not answer the fundamental question Nishioka presents, which is how an above-average hitter with a great defensive reputation can look so hopeless overseas, but nothing will; every move prevents its own set of risks, and we have less information about this risk than we do, say, how a player will adjust after moving from the AL to the NL.
But it's hard to imagine it was something systemic, and not personal, that caused such a collapse in Nishioka's numbers and his early exit from the states, given the relatively orderly transition of other Japanese infielders like Tadahito Iguchi and Akinori Iwamura. Whatever it was, the player the Athletics have signed is considerably better than the one that warned other teams off of him.
He's also considerably better than Ty Wigginton, but that's something I'll have to learn to deal with.