MIGHTY CASEY: Three years ago, USC's Casey Burrill could not even throw a baseball after he injured a ligament supporting his shoulder. The former Hart High standout needed reconstructive surgery--the same operation Dodger pitcher Orel Hershiser underwent about six months earlier--but there was no guarantee he would be able to throw with strength or precision. . . . But Burrill has made it all the way back. The Trojan catcher is enjoying a spectacular senior season in which he is earning recognition as one of the top players in the nation (C8).