Matt Cassel took a team(that the year before went 16-0 and lost the super bowl) to a 11-5 record. They became the only team to go 11-5 and not qualify for the playoffs. Cassel didn't get the chance to win/lose in the playoff with a damn fine team.
Alex Smith's 2011 team went 13-3 and won one playoff game(after a first round bye). A first year starting QB in only his second year in the league. Took that team the next year to 13-3 and won two playoff games(after a first round bye) to the super bowl.
Too close for comfort for me.