First, you have to realize that much of the Lehigh Valley roster may be turned over due to minor league free agency. Some of the stars of the 2011 club could be re-signed, like veteran minor league outfielder Rich Thompson, but others may be replaced by either younger prospects or other minor league free agents.
Yes, we have Freddy Galvis and Domonic Brown returning, but for very different reasons. In Galvis' case, it's because it's likely the Phillies will want him to have more minor league work, no matter how the Jimmy Rollins contract situation plays out. For Brown, there are no guarantees of a spot with the big league club in 2012 and if he doesn't turn things around, he'll likely start the year with Lehigh Valley.
Keep in mind too, that some of these prospects may get a long look with the major league club. Put Justin De Fratus and Joe Savery in that group.
Left-Handed Pitchers: Jacob Diekman (RDG), Joe Savery (LV)
Catchers: Tuffy Gosewisch (RDG)
Third Basemen: Carlos Rivero (RDG)
Shortstops: Freddy Galvis (LV)
Outfielders: Domonic Brown (LV)