Brett Favre, Adrian Peterson and the Minnesota Vikings were anything but perfect. The Vikings couldn't gain a half-yard when it might have turned the game, then watched the Steelers' big-play defense end their unbeaten season with two long touchdown returns in the final 6 1/2 minutes. LaMarr Woodley's 77-yard fumble return and Keyaron Fox's 82-yard interception return on turnovers…