Hunter, who will pitch out of the bullpen, made one relief appearance at Bowie in his latest Minor League stint.
Over his five-year career, Hunter has made 13 relief outings, going 1-1 with a 5.06 ERA in 21 1/3 innings of work.
Manager Buck Showalter is hoping Hunter, who started 20 games for the Orioles this season, can make a smooth transition to the bullpen, just as lefty Brian Matusz did.
"Tommy, he's going to give us some potential length in the bullpen," Showalter said about the 26-year-old. "Some people think this might be where he ends up. We'll see, because he has pitched well out of the bullpen in the past.
"He is a guy that has experience up here at a young age. His stuff plays up a little bit out of the bullpen. We'll see if that continues at this level."
Showalter believes his velocity could be up a notch as a reliever, as Hunter reached 96 mph on the radar gun in his last outing at Bowie.
In his 20 starts, Hunter went 4-8 with a 5.71 ERA. He's pitched 4 1/3 innings in relief, allowing six earned runs on 10 hits and two walks, with four strikeouts.