Martinez was optioned to Triple-A Round Rock on Wednesday, Stefan Stevenson of the Fort Worth Star-Telegram reports.
After yielding 12 runs over 9.1 innings in a pair of starts last week, Martinez's chances of sticking around in the rotation were never great, but it appeared he might have gained some hope after Andrew Cashner (neck) was scratched from his scheduled start Tuesday against the Mets. It remains unclear if Cashner will require a trip to the disabled list, but even if that's the case, the Rangers seem content to explore other starting options, as Martinez has proven ill suited for a rotation spot. He's run up a 5.38 ERA and 1.37 WHIP over 80.1 innings in the big leagues this season.