Not that Wilner is any kind authority on anything related to baseball, but all the signs point to him being a reliever. Another guy who is now a reliever is John Stilson.
I've said this on this thread already, but when a guy has been throwing all ST, is kept in ExST pitching in games and then makes his first appearance in class A and only throws 1 inning, that means he's being used as a reliever. Look at Sean Nolin, stayed back in ExST because of an injury (groin?), and on his first start went 3+. On his 2nd start went 6.
This team could use a reliever also. Maybe McGowan and Stison/Carreno can provide options as relievers. Look, Santos may be done for the year. Rogers is not a 7/8th inning guy. Delabar has struggled with command and would be the only righty Gibbons would be comfortable with late in games. At least guys like McGowan, Stilson, Carreno would give the team more righty options to complement the 3 lefties to match up against teams.