During a critical play-off game in 1975, Dallas Cowboys' quarterback Roger Staubach needed a last-second touchdown to win the game. With only enough time for one play, Staubach sent all of his eligible receivers downfield while he threw a long, arcing pass towards the end zone. Teammate Drew Pearson caught the ball and scored the winning touchdown. During a post-game press conference, Staubach, a devout Catholic, said he whispered a "Hail Mary" prayer as he released the ball. Since that time, any last-second pass towards the end zone has been called a Hail Mary.

There are a number of things which could happen during a Hail Mary pass, and most of them are bad for the offense. Defenders are usually aware of the few seconds remaining on the game clock, as well as the offensive team's need for a touchdown. If the offense is out of field goal range, the quarterback won't risk a running play or short pass. A Hail Mary pass is the last, best option for a team with no means to stop the clock and too many yards to gain on one play.

During a Hail Mary pass play, the offensive line-up may change to as many as five eligible receivers, all of whom run downfield as quickly as possible. If there are any running backs on the field, they work to protect the quarterback from any blindside rushes. The quarterback rarely has enough time to select a specific receiver, so he will choose to loft the ball in a high arc to give receivers a chance to reach the end zone.

Meanwhile, the defensive team also adjusts their strategy to break up a Hail Mary pass play. Defensive backs are assigned to different zones on the field, not man-to-man coverage. Three or four defensive linesmen may put pressure on the quarterback by rushing straight at him. If the quarterback does launch a Hail Mary pass, it is up to the defensive backs to cover the receivers or intercept the ball themselves. The defense must not interfere with the receiver before the ball arrives, however, or the officials may charge them with pass interference.

There are two outcomes of a Hail Mary which will help the offense. With any luck, or divine intervention, an eligible receiver will catch the ball and cross the plane of the end zone for a touchdown. If that doesn't happen, a defensive player may cover a receiver too aggressively, leading to a pass interference call. Since a game cannot end on a defensive penalty, the ball would be placed at the point of illegal contact, usually within a few yards of the goal line in a Hail Mary situation. The offense would have one final opportunity to score a touchdown.

The Hail Mary passing play has a very low percentage of success, but there have been some memorable examples of Hail Mary passes that actually worked. Many football fans still remember a 1984 game between Boston College and Miami of Florida. Boston College's quarterback Doug Flutie launched a Hail Mary pass during the last seconds of the game and defeated the Miami Hurricanes. Miami's defense assumed that Flutie would not have enough strength to send the ball into the end zone, so they were prepared for a shorter pass. Instead, Flutie's Hail Mary sailed into the end zone and into the hands of his receiver.