The Orioles will call up a reliever from Triple-A Norfolk tomorrow to replace first baseman Rhyne Hughes on the 25-man roster.
Alberto Castillo and Kam Mickolio are on the 40-man roster. The choice doesn't appear to be non-roster pitcher Dennis Sarfate, though he hasn't allowed an earned run in 7 2/3 innings and International League batters are 1-for-26 against him.
Update: Mickolio is dealing with a sore back, so you can eliminate him from consideration. Look for Castillo to be in uniform tomorrow.
He certainly knows the way to Camden Yards.