I'm told that Triple-A Norfolk left-hander Alberto Castillo and right-hander Frank Mata will join the club later today as the two roster moves to take the spots of Koji Uehara and Alfredo Simon, who are both headed to the disabled list.
Castillo is 0-0 with a 3.38 ERA in eight games for the Tides, and 1-0 with a 12.79 ERA in nine games with the Orioles. This will be his third stint with the Orioles this season. Castillo could become the main situational lefty if the club decides to use Will Ohman as the closer.
Mata, 26, is 2-1 with a 1.86 ERA and eight saves for Norfolk. Signed in November as a minor league free agent, Mata has never pitched in the big leagues. The Orioles will need to open up a 40-man roster spot for him.
One of the two pitchers summoned to the big leagues today will be the likely candidate to return to the minors on Saturday if the Orioles decide to move David Hernandez to the bullpen and bring up Chris Tillman or Jake Arrieta to take his place in the rotation.
Arrieta is scheduled to pitch in a couple of hours for Norfolk, so unless he is scratched or removed after one or two innings, you can probably take him out of the equation for Saturday's start with the Orioles. There is no way the club would ask him to make his big league debut on three days' rest.
In other news, Triple-A Norfolk outfielder Nolan Reimold will be away from the team for a couple of days after the birth of his first child, a baby girl.