Ziegler, 36, was acquired by the Red Sox Saturday from the Arizona Diamondbacks in exchange for minor league right-handed pitcher Jose Almonte and minor league infielder Luis Alejandro Basabe. The right-hander is 2-3 with a 2.82 ERA (12 ER/38.1 IP) in 36 relief appearances this season, converting 18 of 20 save opportunities and finishing 30 games with 27 strikeouts and only one home run allowed. Originally signed by Philadelphia as a 20th-round selection in the 2003 June Draft, Ziegler is 32-24 with 81 saves and a 2.49 ERA (157 ER/567.0 IP) in 571 career appearances, all in relief with the Oakland A's (2008-11) and Diamondbacks (2011-16). Born in Pratt, KS, Ziegler converted 43 consecutive save opportunities from May 29, 2015 to June 20, 2016, the longest such streak in Arizona franchise history and the seventh-longest in major league history.
O'Sullivan, 28, has made five appearances (four starts) for the Red Sox in two stints with the club this season, going 2-0 with a 6.75 ERA (16 ER/21.1 IP). Boston has won each of his four starts, most recently a pair of 5.0-inning performances on July 8 against the Rays and July 3 versus the Los Angeles Angels of Anaheim. Originally selected by the Angels in the third round of the 2005 June Draft, O'Sullivan is 13-23 with a 6.01 ERA (216 ER/323.2 IP) in 71 games (56 starts) over parts of seven major league seasons with the Angels (2009-10), Royals (2010-11), Padres (2013), Phillies (2014-15), and Red Sox (2016). Signed by Boston as a minor league free agent on December 5, 2015, O'Sullivan has also made 11 starts at Pawtucket this season, going 6-2 with a 2.79 ERA (22 ER/71.0 IP) and 51 strikeouts against 10 walks.