I understand when people look at some of the poor decisions Jake made that resulted in critical turnovers, like v. Kansas, and wonder what might have been with a different QB. I think those are fair concerns when suggesting that we might have been able to go undefeated if we had a QB that was even better than Retzlaff.
However, Jake does some things that he doesn't get as much credit for as I think he should. First, he is a very good runner. Second, and somewhat related, he is very, very good with his option play. While he had some critical turnovers at key moments due to interceptions, he also had some critical conversions with his feet and option pitches that helped us win games.
A lot of "better QBs" might still not be as successful as Jake Retzlaff if they were inserted into our offense because they can't do those things anywhere near as well as Retzlaff can.
I do think there are QBs that might have been better and led us to an undefeated season, but not many and Retzlaff has still been pretty great — we could do a lot worse.