"This one he said was nothing like the [previous] two," manager Buck Showalter said. "We won't use the 'H' word. I'm hoping it was more of a cramping than a hamstring. I'm not going to really address his availability tonight, but we think it's something that should manage itself shortly. Maybe by 9 o'clock."
Miller, who was acquired from the Red Sox at the Trade Deadline, has posted a 1.42 ERA in 13 appearances since joining the Orioles. He gave up only his second earned run on Monday. Including his time in Boston this year, the lefty is 5-5 with a 2.13 ERA and 86 strikeouts.
Miller spent time on the disabled list in both 2012 and '07 with hamstring injuries.
"We've got an idea of what's going on there," Showalter said Tuesday. "He had a little tweak last night on the last pitch. Only time he felt it."
Brittany Ghiroli is a reporter for MLB.com. Read her blog, Britt's Bird Watch, and follow her on Facebook and Twitter @britt_ghiroli. David Wilson is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.