Martinez was recalled from Triple-A Round Rock on Tuesday, Jeff Wilson of the Fort Worth Star-Telegram reports.
Tom Wilhelmsen lost his spot on the roster after a six-run blowup Monday and Martinez was called up in a corresponding move. He will presumably work out of the bullpen for the time being. Martinez struck out 20 in a recent two-start stretch down at Round Rock, but he's averaged just 5.2 K/9 in 54 career appearances (45 starts) at the major league level.