Martinez is scheduled to start Sunday's game in Baltimore.
Martinez looked as though he might have been at risk of moving to the bullpen after the Athletics summoned Ken Waldichuk from Triple-A Las Vegas to start Thursday, but at least for this week, Oakland will expand their rotation to six men to open up spots for both rookies. Though Martinez owns an unremarkable 5.28 ERA and 1.34 WHIP over six outings with Oakland this season, he turned in the best start of his young career his last time out Aug. 28, when he limited the Yankees to one run while allowing five baserunners and striking out career-high six batters over 5.1 innings.