The Red Sox will designate right-handed reliever Clayton Mortensen for assignment, tweets Pete Abraham of the Boston Globe. A roster spot was needed to make room for the call-up of Jonathan Diaz, who will man third base while Stephen Drew recovers from a hamstring injury suffered last night.
Mortensen, 28, has thrown 30 1/3 innings for the Sox this season, posting a 5.34 ERA to go with just 6.2 K/9 versus 4.7 BB/9. He had a solid campaign last year, when he split time between the bigs and upper minors. While throwing for Boston in 2012, Mortensen sported a 3.21 ERA in 42 innings on the back of 8.8 K/9 against 4.1 BB/9.
Diaz, meanwhile, will make his big league debut at age 28. In 917 career plate appearances at Triple-A over five seasons, he has a .239/.358/.317 line. Diaz has logged most of his innings up the middle, though he does have 47 minor league games under his belt at third.