Tazawa, 29, made 61 appearances out of the Red Sox bullpen last season, going 2-7 with three saves and a 4.14 ERA (27 ER/58.2 IP). He led Red Sox relievers with 56 strikeouts and 16 holds. The right-hander, who appeared in at least 60 games for the third straight year, did not allow a run in 46 of his 61 outings (75%). A native of Yokohama, Japan, Tazawa posted a 1.33 ERA (4 ER/27.0 IP) with a .179 opponent batting average (17-for-95) over his first 29 games of the season through June 11. After that point, he gave up 23 earned runs in 31.2 innings (6.54 ERA).
Signed by Boston as an international free agent in December 2008, Tazawa is 14-18 with four saves and a 3.47 ERA (101 ER/262.1 IP) in 249 career major league outings, including four starts, all with the Red Sox (2009, 2011-15). Since 2013, he ranks eighth among American League relievers with 57 holds.
With today's agreement, left-handed pitcher Robbie Ross Jr. is the only remaining unsigned Red Sox player eligible for salary arbitration.