This is from Len Pasquarelli's Insider Tip Sheet and much of an eye opener, I thought.

* The list: Chicago quarterback Rex Grossman's regular-season passer rating of 73.9 is the worst for a Super Bowl starter since John Elway of Denver went into Super Bowl XXIV after the 1989 season with an efficiency mark of 73.7. But Grossman is actually in pretty good company. Here are the Super Bowl starters who had worse efficiency ratings than Grossman, and please note that seven of them are Hall of Fame members: Vince Ferragamo, Rams, 49.0 (Super Bowl XIV); Terry Bradshaw, Steelers, 55.2 (Super Bowl IX); David Woodley, Dolphins, 63.5 (Super Bowl XVII); Bart Starr, Packers, 64.4 (Super Bowl II); Johnny Unitas, Colts, 65.1 (Super Bowl V); Tony Eason, Patriots, 67.5 (Super Bowl XX); Len Dawson, Chiefs, 69.9 (Super Bowl IV); Bob Griese, Dolphins, 71.6 (Super Bowl VII); Joe Namath, Jets, 72.1 (Super Bowl III); Jim Plunkett, Raiders, 72.9 (Super Bowl XV); and Elway, Broncos, 73.7 (Super Bowl XXIV).