Martinez will return to the majors and start Friday against the Athletics, Jeff Wilson of the Fort Worth Star-Telegram reports.
The Rangers are sending Tyson Ross to the bullpen, and Martinez will take his place. Martinez had a poor 5.59 ERA and 1.66 WHIP in 38.2 innings for Texas earlier this season, but he's been dominant for Triple-A Round Rock, where he has a 2.15 ERA and 0.91 WHIP over six starts. Expect an official move to be made after Thursday's game.