This information comes to us from Nikkan Sports - if you don't speak Japanese (and my one semester of evening classes in that area appear largely unsuited to the task), then fortunately, Patrick Newman of NPB Tracker is here to help:
Hiroyuki Nakajima is already in the States and negotiating with the D-Backs. Seems like a plausible destination for him nikkansports.com/baseball/news/…— Patrick Newman (@npbtracker) November 20, 2012
In his career, Nakajima's line is .302/.367/.475. He has played 11 years in Japan, all of them with the Seibu Lions, but started early, and so only turned 30 in July. Hiroyuki is a seven time NPB All-Star and three-time Best Nine winner (it's like the MVP, but awarded at each position, which is kinda cool). However, he was notably absent from both this year, despite hitting .311, with an OPS 46 points better than the previous season, where he was an All-Star and Best Nine. Was he being punished in some way for his actions the previous winter?
For his team had "posted" him, the process by which major league teams can bid for the services of Japanese players. The Yankees won that, with a bid of $2 million: however, that only gave them the right to negotiate a contract with Nakajima, and no such deal was reached, in part, because he'd have been on the bench (the Yankees already having a shortstop - Derek something?). As a result, Nakajima remained with Seibu though New York didn't lose their money [still, let's all pause to laugh at the Yankees: hahaha!]. One can imagine this could have been seen as an embarrassment to NPB, but I'm really just speculating.
Anyway, having been posted once, he doesn't have to go through the process again, and is now a free-agent, able to sign with anyone. The Diamondbacks are not the first major-league team to whom he has been linked this off-season, with the Oakland Athletics apparently also interested. But one thing to note: though he was a regular shortstop in Japan, there's speculation he might be moved, Newman saying, "No one seems to think he can stick there in MLB," and suggesting 3B might be a better fit for Nakajima. He does have some pop, hitting 13 homers last year, with four 20-HR seasons under his belt.
As someone pointed out, the track records of Japanese infielders in MLB aren't really too much to write home about. The high-water mark to date is Tadahito Iguchi, who posted a 93 OPS+ over four seasons from 2005 to 2008. The two most recent examples, Tsuyoshi Nishioka and Munenori Kawasaki, who both played last season, were a good deal worse at 41 and 35 respectively. Nakajima does have somewhat better offensive numbers: his career OPS in Japan is .834, compared to .790 for Nishioka and .721 for Kawasaki. But, whether he plays 3B or SS, it'd still likely be the upper end of expectations for him to match the 96 OPS+ we got from Stephen Drew in his time with Arizona.
As you may remember, Derrick Hall and other team executives made a trip to Japan earlier this year, and it seems one of the aims was to strengthen the Pacific rim as a possible source of talent for the club. Reliever Kyuji Fujikawa is another name with which we have reportedly been linked, so it'll be interesting to see how this develops.