Hunter, who walked off under his own accordance after head athletic trainer Richie Bancells came out to the mound, is considered day to day for what would be his final start of the season.
"It got pretty tight," said Hunter, who left after Mike Aviles grounded out. "It was one of those things, been lingering around all year. It got really tight and it was just one of those things. I needed to come out."
Hunter was charged with four runs before exiting, three of which came almost singlehandedly from Red Sox outfielder Carl Crawford, who tripled and scored in the third and doubled in a pair of two-out runs off the Green Monster in the fourth. A reliable innings-eater for the Orioles since being acquired from Texas, Hunter said he felt discomfort during the Aviles at-bat and didn't want to push things.
"That's when you get hurt," said Hunter, who suffered the same injury with the Rangers in Spring Training and didn't make his first Major League appearance until July 2. "[I'll] get some ice, get some treatment and hopefully be ready to go in five days."
Brittany Ghiroli is a reporter for MLB.com. Read her blog, Britt's Bird Watch, and follow her on Twitter @britt_ghiroli. This story was not subject to the approval of Major League Baseball or its clubs.