Red Sox select infielder Jonathan Diaz to active roster

The Boston Red Sox today selected infielder Jonathan Diaz to the active major league roster from Triple-A Pawtucket. To make room for him on the 40-man roster, right-hander Clayton Mortensen was designated for assignment. Diaz will wear No. 76 and will be available for today's 4:05 p.m. game against the Blue Jays at Fenway Park.

Executive Vice President/General Manager Ben Cherington made the announcement.

For Diaz, 28, this is his first career major league stint. He has appeared in 55 games with Pawtucket this season and has played at second base (29 games), shortstop (13 games), and third base (12 games). The right-handed hitter is batting .242 (44-for-182) with eight doubles, two triples, two home runs, 21 RBI, 24 walks, 30 runs scored, and six stolen bases this season. Signed by the Red Sox as a minor league free agent on December 12, 2012, he owns a .357 on-base percentage in eight career minor league seasons with the Blue Jays (2006-12) and Red Sox (2013).

Mortensen, 28, is 1-2 with a 5.34 ERA (18 ER/30.1 IP), 16 walks, and 21 strikeouts in 24 games for the Red Sox in 2013. He missed time on the disabled list from June 11-25 due to a right groin strain and appeared in three rehab games with Pawtucket, posting a 4.50 ERA (2 ER/4.0 IP) with two walks, and four strikeouts. Acquired by the Red Sox from the Rockies in exchange for shortstop Marco Scutaro on January 21, 2012, Mortensen owns a 6-11 career record with a 4.68 ERA (87 ER/167.1 IP) and 112 strikeouts in 74 career major league games (13 starts) with the Cardinals (2009), A's (2009-10), Rockies (2011), and Red Sox (2012-13).