There are a lot that never started at USC, if you mean QBs that went to NFL without starting at USC then Matt Cassel is one.
Tom Brady and Matt Cassel.
Matt Cassel, Tyler Palko, and Brodie Croyle.
Matt Cassel was traded to the Kansas City Chiefs
Backup quarterbacks have been Rohan Davey, Matt Cassel, Brian Hoyer, Vinny Testaverde, Matt Gutierrez, and Ryan Mallett.
Sid Cassel was born on July 24, 1897, in Leeds, Yorkshire, England, UK.
Tom Brady,Brett Favre,Payton Manning,Tony Romo,Kurt Warner,Eli Manning,Randy Moss,Matt Cassel,Steven Moss,Mark Ocho
USC he was Leinarts backup
Matt Cassel.
Matt Cassel has: Played Himself - New England Patriots Quarterback in "NFL Monday Night Football" in 1970. Played Himself - Kansas City Chiefs Quarterback in "NFL Monday Night Football" in 1970. Played Himself - Telephone Interviewee in "Mike and Mike in the Morning" in 2005. Played Himself - New England Patriots Quarterback in "NBC Sunday Night Football" in 2006. Performed in "Kenny Powers: The K-Swiss MFCEO" in 2011.
Last ten Patriots quarterbacks to start games - Tom Brady Matt Cassel Drew Bledsoe Scott Zolak Tommy Hodson Hugh Millen Marc Wilson Doug Flutie Steve Grogan Tony Eason
The only one I know of is Matt Cassel, who was a backup quarterback at USC to Carson Palmer (2002) and Matt Leinart (2003-2004), both of whom were Heisman Trophy winners. He did start one game, but that was at halfback rather than quarterback. He was drafted in the 7th round by the New England Patriots and now plays for the Kansas City Chiefs.