If you go back to OU top 100 freshman from Hollis Price forward, I believe they all contributed as freshman with the exception of two forwards. I think those players were Hollis Price, Drew Lavendar, Lawrence McKensie, Tony Crocker, Kevin Bookout, Keith Clark, Cam Clark, Blake Griffin, TMG, Willie Warren, Tiny Gallon, Steven Pledger, Andrew Fitzgerald, Longar Longar and Larry Turner. 8 of those guys started as freshman. Price, McKensie, Pledger, Keith Clark and Fitzgerald all constirbuted as true freshman. History would suggest both Hield and Hornbeak will contribute. Only one guy on that list really didn't contribute and that was Larry Turner.
It should be noted that some had Ray Willis as a top 100 player and he really didn't contribute much at OU. However, you may counter that with guys like Godbold and AJ that were not top 100 players and made significant contributions as freshman. One other top 100 player that never contributed was TJ Taylor. He got a concussion and then left the program.