After missing a week with elbow stiffness, the pitcher exited Tuesday's game against the Blue Jays with a mild left hamstring strain. He limped off the JetBlue Park field after only three pitches.
"That seems to be mild in nature," Red Sox manager Bobby Valentine said of the injury. "But we'll know more [Wednesday]."
With the latest setback, Miller's chance at earning a spot in the starting rotation and getting stretched to five innings took a significant hit. When asked if the injury made it harder for Miller to compete, Valentine nodded.
"For a starting job, yes," he said.
In his abbreviated appearances this spring, Miller has fanned six of the 10 batters he's faced.