I don't think Boston goes after Tanaka. Maybe we should if you were looking at iit with a structly clerical, administrative fashion, but if you think we should be the one who's rolling high to bring in Tanaka, riddle me this: Which one of Lester, Buchholz, Lackey, Peavy and Doubront isn't pitching if Tanaka is?
That's a question with 5 bad answers.
In a vacuum, without finance and opportunity costs in the picture, you might consider Doubront, but even Doubront isn't a bad bet to produce at an average or better rate next year, meaning anything you gain from Tanaka is gained over a stable of pitchers that's already pretty good -- not the best time to be sinking a lot of money into pitching. Especially when we already have to clear Dempster off the payroll this year.
There's better ways to use the same money, such as a short term flier on Beltran to help ballast out our offensive outfield, or looking at options at third base, shortstop and catcher to shore up potential weaknesses there due to the inexperience of the players we're currently going into the season with at those positions. And there's every chance that a more conventional #6 is closer to a match for our needs, for example Chad Gaudin, who can probably be had far less expensively.
I'm more interested in innings than ace-type performance, to be frank about it, and that's exactly what I'm less sure a Japanese import is going to be able to give us in year one as he adjusts to the different rotation model. We need 200 innings far more than we need a high ERA+ number, and we can get that for a fair bit less than we'd pay for Tanaka..