Andrew Miller – Acquired as a free agent and eventually traded to Baltimore for Eduardo Rodriguez. He converted from a starter to the bullpen and is now one of the élite specialist in the game. Miller’s ERA is well under 2.00 with Baltimore, New York, and now Cleveland. His postseason ERA is 0.98.
Koji Uehara – Signed to add depth to the bullpen and became a legend with his 2013 season when Boston needed a closer. Koji finished 2013 with a 4-1 record, 1.09 ERA and 21 saves. He tacked on 26 saves in 2014 and 25 in 2015. In four seasons with the Red Sox, Koji had 79 saves and a 2.19 ERA. Uehara signed with the Cubs as a free agent.
Mark Melancon – Arrived in Boston from Houston for Lowrie. He did nothing for the Red Sox and was traded to Pittsburgh for Brock Holt. Melancon led National League with 51 saves in 2015. Now he’s with the Giants.
Alex Wilson – A throw-in with Cespedes in the Porcello trade with the Tigers. Wilson has become an exceptional bridge reliever. Wilson finished his two partial seasons in Boston with a 2-1 record.
Matt Albers – Albers signed a free-agent deal with the Red Sox in 2010 and was traded to Arizona in 2012. His record in Boston was 6-4 with a 3.81 ERA. How he pitches for the Nationals.
Craig Breslow – Breslow is still tossing. He was traded to Boston in 2012 for Albers. Prior to that he had signed with the Red Sox as a free agent (2006) and yet again in 2015. In five seasons with Boston, Breslow was 8-12 with a 3.80 ERA.
Junichi Tazawa – Signed from the Japan Industrial League, Tazawa left after 2016 as a free agent. He had a solid seven-year Boston run, primarily out of the bullpen as a setup reliever. Tazawa pitched 302 games for the Red Sox with a 3.58 ERA. He allowed only one earned run in 13 postseason games.