I don't have particularly high hopes for any of the trio. Omersa's lack of development last season was extemely disappointing. I was hoping he could build off some encouraging things I saw from him in the MSU game in the NCAA tournament, but it just didn't happen. I think his best role is a very undersized 5 (ala PJ Tucker) who can bother some bigs with his strength, but is athletic enough to switch pick and rolls and give a good effort defensively against anyone 1-5. Obviously he can't shoot like PJ, but having him at the 5 (say when Robbins sits) could allow this team to be uber athletic at times and give the opposition a total different look. He's got to be a lot better in virtually every area than he was as a Sophomore to make that work though. He has a long ways to go to be Miles Tarver, but his athleticism gives him upside.
Sam Freeman underwhelmed even from the viewpoint of bigs (especially lightly recruited ones) take time. He has a huge jump to make just for Pitino to be comfortable giving him 5 minutes in a game that hasn't been decided yet.
Mitchell is really, really thin, views himself as a 3/4, and has had numerous recruiting guys question his motor. He has to become much more skilled to play the role he envisions or really dedicate himself to getting bigger to play inside in the B1G. Out of the 3, he'd be the best redshirt candidate because he arguably has the highest ceiling (given that Omersa is now a JR) and he has the clear need to attempt to add good weight to his frame.
Slightly off topic, but I am not sure we've had a player redshirt (not due to injury or transfer) since Pitino took over. I am probably misssing a number of players but last redshirt I remember was Kevin Payton under Monson?