Athletics manager Mark Kotsay said Martinez will be called up from Triple-A Las Vegas to start Thursday's game against the Mariners in Seattle, Matt Kawahara of the San Francisco Chronicle reports.
The 25-year-old right-hander will be entering the rotation as a replacement for Jared Koenig, who was optioned to Triple-A over the weekend. Martinez has delivered a strong 18.1 K-BB% over 13 starts for Las Vegas this season, but pitching in the hitter-friendly Pacific Coast League has likely played a part in him turning in an underwhelming 5.63 ERA and 1.41 WHIP. He'll be getting the call to Oakland for the second time this season after he tossed 5.1 scoreless frames in a winning effort May 10 against the Tigers in his MLB debut.