Hanrahan will give the Sox multiple options at the end of games.
Shortly after that, ESPN.com's Jim Bowden started giving the details to the actual deal between the two teams.
The main pieces to the swap look to be Hanrahan coming to Boston with the recently acquired Jerry Sands and minor league prospect Stolmy Pimentel going to Pittsburgh.
CBSSports.com's Jon Heyman later reported that the deal would involve six players in total, with the Pirates receiving four players and the Sox receiving two.
Edes later mentions that reliever Mark Melancon might be one of the players headed out of Boston.
Unless the fourth player is someone special from the Sox' farm system, Boston looks to be getting the best player in the deal.
The 31-year-old Hanrahan has been an effective closer for the Pirates and will certainly give the Sox a ton of options to close games next season.
This move doesn't immediately mean that current closer Andrew Bailey will be traded, but more the Red Sox were unsure about what they saw from Bailey and wanted more certainty at the end of games.
Do you like the Sox's deal for Hanrahan?
If that's the case, having potentially the deepest bullpen in the majors will be a major asset.
Sox manager John Farrell will be able to ask the starters for six innings and give the bullpen the lead with a chance to win the game.
It is a low-risk move in the fact that the Sox are trading players who didn't really factor into their long-term plans and will likely clear four spots from their 40-man roster with the deal as well.
A deal like that for a two-time All Star who has saved 76 games over the past two seasons seems too good to pass up. This will be like the Bobby Jenks move, but much better.
The only potential downside to the deal is Hanrahan's 2012 average of over five walks per nine innings; that is asking for trouble at Fenway Park and could spell trouble in Boston.
Hanrahan's career strikeout average of 9.9 K/per nine innings gives the Sox someone who can get a strikeout when needed.
If they can get Daniel Bard back on track, the Sox could have a suddenly dynamic bullpen.
Between Hanrahan, Bard, Bailey, Craig Breslow, Alfredo Aceves and the recently signed Koji Uehara, the Sox will have six pitchers who have all held left-handed batters to a career batting average at .226 or below.
The Sox are going to make a lot of trips to the mound next season, which could turn out to be a good thing.
Statistics used from Baseball Reference.