Per the Rangers beat writers, Justin Grimm and Randy Wells have been informed that they will be starting the season in AAA.
In conjunction with the news that Robbie Ross will be starting the season in the Rangers' bullpen, this means that Nick Tepesch will apparently be the team's fifth starter.
Derek Lowe could, theoretically, but in the mix for the fifth starter job, but after yesterday's outing, I doubt the Rangers are going to trust him to go through the lineup more than once.
The other possibility is that the Rangers could trade for Rick Porcello or sign Kyle Lohse. However, Lohse is going to need to essentially go through spring training, and will likely be several weeks away from being able to start in the majors.
Tepesch was considered a long-shot for the fifth starter job coming into camp, but with Martin Perez and Kyle McClellan getting hurt, Justin Grimm having an awful spring, and no one else stepping up, Tepesch has been able to claim the job.