The time for the Red Sox to rework their bullpen came after the 2011 season. After the tremendous September collapse that led to the departure of manager Terry Francona and GM/ President Theo Epstein. Leaving via free agency was closer Jonathan Papelbon to the Phillies and questions rose over whether 2011 8th inning pitcher Daniel Bard was going to be a starter. That led the Red Sox to make the trade for Oakland's Andrew Bailey, giving up OF Josh Reddick in return. They also traded for Houston's Mark Melancon, giving SS Jed Lowrie to the Astros as part of the deal. Returning to the Red Sox bullpen in 2012, were RHP Matt Albers, RHP Alfredo Aceves and two lefties, Andrew Miller and Franklin Morales. The first wise decision made was to make Miller, who had been a starting pitcher, to a reliever. The addition of free agents Vincente Padilla and Scott Atchison completed what was expected to be a solid pen. Bailey, of course, got hurt after pitching in just 19 games (1-1. 7.04, 6 saves). Melancon (0-2, 6.20, 1 save in 41 games) was horrible and Aceves (2-10. 5.36, 25 saves, 69 games) and Padilla (4-1, 4.50, 1 save, 56 games) were not much better. Albers, coming off a good 2011 season, finished at 2-0, 2.29 in 40 games before he was traded during 2012.
Miller was the bright spot, as he established himself as a dependable LHP that can throw 95 plus. He finished 2012 at 3-2, 3.35 in 53 games. In addition to Miller, the Red Sox got some breaks towards to middle to end of the season. Tazawa returned from his Tommy John surgery and finished strong at 1-1, 1.43 in 37 games. Breslow came over from Arizona in the trade for Albers and was solid (1-0, 2.70 in 23 games). Morales split the season between the rotation and the bullpen (3-4, 3.77, 1 save in 37 games, 9 starts). Atchison (2-1, 1.58 in 42 games) was solid, but had arm issues that limited his availability. Veteran Rich Hill (1-0, 1.83 in 25 games) helped out for a little bit as did Clayton Mortensen (1-1, 3.21 in 26 games).
Overall, the Red Sox bullpen needed an overhaul. The expected return of RHPs Bailey and Tazawa and lefties Miller and Breslow gave the team something to start with. Then the Red Sox made the deal with the Pirates to get All Star closer Joel Hanrahan, who had come off back to back All Star season where he finished with 40 and 36 saves, respectively. The Red Sox made a then quiet signing of RHP Koji Uehara, to a 2 year deal. I remember talking in the offseason how the Red Sox had a solid top 4 in their bullpen that was as good, if not better, as any team in baseball (Hanrahan, Bailey, Uehara, Miller). Of course, we all know what happened. Hanrahan (0-1, 9.82, 4 saves in 9 games) was lost early in the season to Tommy John. Bailey (3-1, 3.77, 8 saves in 30 games) stuck around a little longer than 2012, but was done for the season by July 12th. Miller (1-2, 2.64 in 37 games), a one time top prospect LHP that was traded to the Marlins for Miguel Cabrera, had his season cut short by July 6th. So, by July 12th, 3 of the 4 pitchers to make the bullpen so solid were done for the season.
For the 3rd time in 2 seasons, the Red Sox needed to make major adjustments to their bullpen. Uehara, by default, was moved into the closers role. Tazawa, who had been pitching in more important spot, slid into the 8th inning spot. And Breslow, who had been the typical LOOGY since before his arrival in Boston, took Miller's spot in the 7th inning. Uehara took his game to another level, finishing at 4-1, 1.09, 21 saves in 73 games. His postseason was even better as he was 1-1, 7 saves giving up just 1 run in 13 2/3 IP, 7 hits, 0 BB and 16 Ks. Tazawa (5-4, 3.16 in 71 games) and Breslow (5-2, 1.81 in 61 games) were solid. Lefties Morales (2-2, 4.62 in 20 games, 1 start) and Matt Thornton (0-1, 3.52 in 20 games), acquired in deal with the White Sox chipped in as well as righties Mortensen (1-2, 5.34 in 24 games), Brandon Workman (6-3, 4.97 in 20 games, 3 starts) and Alex Wilson (1-1, 4.88 in 26 games).
Most teams change their bullpens up from year to year. Few teams that have to change it up twice in a season (and 3 times in 2 years) have any effectiveness, let alone the success the Boston Red Sox had in 2013. Many things worked out for this team on their way to a World Series Championship, but if it wasn't for the bullpen, they would not have won the whole thing.