John Blake just tweeted that the Rangers' probable starters for the three game set against Boston which begins on Tuesday are Justin Grimm, Alexi Ogando, and Derek Holland.
Ogando, who had a successful rehab outing on Friday, was expected to re-join the rotation this week, although the exact date was still in the air. With the Rangers having an off-day on Monday, Ogando could have been pushed all the way back to Saturday, with the other starting pitchers staying on their regular rest.
With Ogando being activated, one of the current eight relievers will need to be sent down. The most likely candidate would seem to be Ross Wolf, who was called up to make an emergency start on May 22, and has been in the bullpen ever since. Other possibilities would be optioning Joe Ortiz, who has not been sharp after a strong start to the season, or dropping Michael Kirkman from the roster. Because Kirkman is out of options, he'd either have to be designated for assignment or put on the disabled list.