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12/03/10 12:44 AM EST

Okajima non-tendered by Red Sox

BOSTON -- Hideki Okajima, the lefty reliever who was vital to Boston's World Series championship in 2007, was non-tendered by the Red Sox before Thursday's 11:59 p.m. ET deadline, making him a free agent for the first time in his Major League career.

Okajima was a key piece of Boston's bullpen in his first three Major League seasons, but struggled mightily in 2010, posting a 4.50 ERA and allowing an opponents' batting average of .314. In his first three years, Okajima never had an ERA higher than 3.39 or an opponents' batting average higher than .242.

The Red Sox still have negotiating rights with Okajima, meaning there's still a possibility he will return for a fifth season in Boston. Okajima earned $2.75 million in 2010, meaning the Red Sox would have had to pay him a salary somewhere in that range if they had tendered him a contract before Thursday night's deadline.

The Sox also non-tendered two pitchers they acquired in November -- left-hander Andrew Miller and right-hander Taylor Buchholz.

Boston did tender contracts to the 21 other players who were unsigned, a list that was highlighted by closer Jonathan Papelbon and outfielder Jacoby Ellsbury.

Okajima, 34, was signed by the Sox as an international free agent on Nov. 30, 2006, coming over from Japan the same year as the more-hyped Daisuke Matsuzaka.

After his first exhibition outing with Boston, Okajima said that he was fine being a "hero in the dark." He lived up to that throughout his rookie year, and was brilliant during the Red Sox's comeback from a 3-1 deficit in the '07 American League Championship Series. It was Okajima who induced a key double play against the Indians with Game 7 on the line.

Okajima also came up big in his second season, allowing no earned runs over five appearances in the ALCS, which the Red Sox lost in seven games.

Okajima is 16-8 with six saves, 85 holds and a 3.06 ERA in 254 games in the Majors.

When the Red Sox acquired Miller from the Marlins on Nov. 12, they were hoping a change of scenery would help him realize the potential the Tigers saw when they made him the sixth pick in the 2006 First-Year Player Draft. It is now unclear if Miller will still be able to try to resurrect his career with Boston.

As for Buchholz, he was claimed off waivers from Toronto on Nov. 15. He combined to go 1-0 with a 3.75 ERA in nine relief outings for the Rockies and Blue Jays last year, when he was coming off Tommy John surgery. Buchholz is 19-21 with one save and a 4.39 ERA in the Majors.

Boston's 40-man roster now stands at 37.

Ian Browne is a reporter for MLB.com. Read his blog, Brownie Points, and follow him on Twitter @IanMBrowne. This story was not subject to the approval of Major League Baseball or its clubs.