The Red Sox have added a potential shutdown reliever to the fold. (Getty Images)

The Red Sox are set to fortify their bullpen by acquiring closer Joel Hanrahan from the Pirates in exchange for outfielder Jerry Sands, right-hander Stolmy Pimentel and two additional players, CBSSports.com's Jon Heyman reports. The Red Sox will also receive an additional player in the deal. Heyman notes the deal might not be finalized until after Christmas because the two sides are still discussing the other players involved. The newest complications are not expected to derail the deal, sources tell Heyman.

Hanrahan, age 31, put up a 2.72 ERA in 59 2/3 innings last season. While he struck out 67 over that span, he also walked 36, all unintentional. His control problems could become more of a concern against the generally tougher offenses of the AL East. Last season, Hanrahan walked 14.2 percent of the batters that he faced. If he doesn't cut that figure, say, in half, then he won't come close to repeating that low ERA.

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Since arriving in Pittsburgh midway through the 2009 season, Hanrahan has an ERA of 2.59 in 238 appearances. He's eligible for salary arbitration this offseason and can become a free agent after 2013.

The addition of Hanrahan, of course, would mean a possible closer controversy in Boston, what with Andrew Bailey on the roster as an arbitration-eligible. Bailey battled injuries in 2012 but is highly effective when healthy. If nothing else, the Red Sox would have options.

As for Pittsburgh's side of things, Sands, 25, had a career .244/.325/.376 line with the Dodgers before being traded to the Red Sox as part of last August's blockbuster. At Triple-A last season, Sands thrived after making some adjustments to his swing and batted .296/.375/.524 in 119 games overall (although those numbers came at Albuquerque, which is an outstanding environment for hitters). Sands has raw power, but it's not sure to what extent it will translate to the highest level. So it's possible he winds up as a player without the bat for a corner spot but without the necessary range to man center. Or it's possible the Pirates have landed a productive regular with right-handed pop.

The 22-year-old Pimentel has a 4.37 ERA and a 1.326 WHIP across parts of six minor-league seasons. In 589 innings, he's struck out 477, walked 191 and given up 57 homers. While Pimentel has always been projectable, the results haven't been there. 

Elsewhere, Heyman reports that Jason Grilli will likely now serve as the Pirates' closer.

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