Masahiro TanakaThe Boston Red Sox must decide whether to be aggressive or hang back while the rest of Major League Baseball dukes it out.

It’s not every day that a potential ace hits the open market, yet that’s exactly the case with Masahiro Tanaka, who officially has been posted by the Rakuten Golden Eagles of Japan’s Nippon Professional Baseball. Every team, including the Red Sox, now has an opportunity to try to sign the right-hander, although landing him likely will be expensive.

In a vacuum, pursuing Tanaka seems like an easy decision. Tanaka could become a front-line major-league starter, and he’s still just 25 years old. Even teams that are rebuilding could decide to take a chance in the hopes that he’ll lead their rotation for many years. The Red Sox have the financial flexibility to be creative, so going after Tanaka certainly is a possibility for Boston despite the club’s surplus of starting pitchers. The question, of course, is if the Red Sox are high enough on Tanaka to abandon their current free-agency philosophy.

General manager Ben Cherington has shown a reluctance to shell out big, long-term contracts to free agents. The contracts given to Carl Crawford, Daisuke Matsuzaka and Adrian Gonzalez have served as cautionary tales. Boston now prefers to hand out shorter contracts, even if it means overpaying in terms of average annual value. This approach has seen the Red Sox sign mid-level free agents like Shane Victorino and Mike Napoli rather than star free agents like Tanaka.

Tanaka could be special. He went 24-0 with a 1.27 ERA with Rakuten in 2013 and actually might be better than Yu Darvish, who has thrived in his first two seasons in Major League Baseball. But Tanaka is expected to command a contract in excess of $100 million — in addition to the $20 million posting fee that must be paid to Rakuten — so going all in on the talented hurler is a major financial commitment.

Click here for Masahiro Tanaka’s top 10 suitors >>

Opinion: Red Sox impacted by Tanaka posting >>

Opinion: Yankees must make strong push for Tanaka >>