A game of the sport of American football is divided into four quarters. The most important quarter is the fourth and last quarter. It is the quarter with the last score, the quarter that decides who wins and who loses the game. A player who makes goals (points) during the fourth and last quarter can win the game for the team, no matter how badly it played during the earlier three quarters. He is a "hero" to his fellow players and the fans. The term could be applied to the business world too. A fourth quarter hero could be the leader who gives outstanding leadership, the employee who makes a large sale or gives a great idea, etc.
"Tide continues to find a fourth-quarter hero" Home - Decaturdaily.com
("Tide" or "Crimson Tide" is the name of the team of the University of Alabama.)