In their first regular season finale they played an awful Colorado team at home and lost as you know. What you may not know is that Colorado won by 3, but during a key drive Colorado was stopped at Utah's 40 after a 3 and 15 incompletion. Colorado was too far away to kick a FG, so they would have punted back to Utah and gotten no points from the drive. Instead, a moronic after-the-play late hit by a Utah CB gave Colorado an automatic first down, which led to a touchdown.

So to answer your question, in a game of inches, a late personal foul penalty can cost your team a game, championship, undefeated season, and trip to a NY's bowl game.