USC Quarterbacks going down-hill?

First u had Carson Palmer, arguably the best USC QB of all time. Then, u had Heisman and Nat. Champ. winning Matt Leinart. Then, u had a good QB in John-David . This past season USC had an above average QB in Mark Sanchez. I know Sanchez had a great game against PSU. But he didn't do anything other than that game that made me say "WOW." I think that the USC QBs r getting worse and worse every year. Any one else think this? or am i just imagining this?