The play's named after a religious plea for intercession. It's a prayer to the heavens as the football is heaved that direction.
The Hail Mary was coined by Roger Staubach after a miraculous throw to win a 1975 NFL playoff game for the Dallas Cowboys.
When all hope is lost, chuck it high and say a prayer.
Just ask Tennessee. The Vols were cooked two weeks ago at Georgia until Joshua Dobbs' moonshot landed in Jauan Jennings' arms to beat the Bulldogs with zeros on the clock. It's the play you never think you'll need until it saves your season.
Nick Saban said Alabama's prepared for such a scenario as it heads to Knoxville for a Saturday visit with the Vols. His 2002 LSU team became part of Hail Mary lore when Marcus Randall tossed the 74-yard, tipped touchdown to Devery Henderson to beat Kentucky.
"They'd already dumped the Gatorade on the coach," Saban said. "So it's not a play you can take for granted. I think a lot of people assume that it's a low-percentage play, they're not going to complete the ball. But when you don't execute and do things correctly, you give them every opportunity to get the ball."
Alabama practices this scenario every Thursday. Still, it's been a while since the Tide defense faced a moment like Tennessee's win over Georgia.
Alabama's offense had a few unsuccessful last gasps at Ole Miss in 2014 and later that season in the Sugar Bowl loss to Ohio State. Tight end O.J. Howard was right there both times.
The Sugar Bowl throw from Blake Sims went into the end zone with two receivers leaping and Howard was standing a few yards in front in case it was tipped forward. The ball went over the heads of DeAndrew White and Chris Black before being intercepted and killing Alabama's title shot.
"I'm more of the trail guy in that situation," Howard said.
The last time a team had a throw to beat Alabama on the final play wasn't quite that deep. Georgia quarterback Aaron Murray's throw was deflected at the line and caught short of the end zone to give Alabama a 32-28 win over the Bulldogs in the 2012 SEC Championship Game.
Three years before that, Auburn quarterback Chris Todd threw one into the end zone only to see a host of Tide defenders swat it down for a 26-21 Iron Bowl win. That was the last true Hail Mary that Alabama's faced on the final play of a game.
"The plan is always to knock it down," Alabama linebacker Rashaan Evans said. 'If you try to catch it, it can tip off your hand and go to your opponent. So, if you can knock it down, that's ways the safest way."
Defensive end Jonathan Allen is well away from that part of the equation.
"For me it's try to get pressure," he said. "It's something we haven't faced this year, but in practice it's my job to get pressure. Hopefully it doesn't come down to that, but we'll deal with that when the time comes."
Not everyone was eager to discuss Hail Mary plans.
"I'd rather not talk about the role of linebackers on that play," linebacker Shaun Dion Hamilton said.
Saban didn't mind.
"Everybody has a philosophy for how to do it," he said. "But, you know, we sort of try to man-match them. We have certain guys that play the ball, we have certain guys that box out. I've lost games on this before. I don't think this is a game that anybody can take for granted, which is sometimes hard to get the players sold on."
Making a competition out of it never hurts.
Alabama defensive back has his version of how the Hail Mary rehearsals go in Thursday practices.
"I don't think they've ever caught one," he said with a proud smile. "We always go against the offense at the end. I don't think they ever ... they like to try and throw in some extra stuff to try and trick us, but it usually doesn't work."
According to research by CougarStats.com, these plays almost never work. Of the 403 final-play throws (30 or more yards) from 2005-13, only 2.5 percent were successful. There were 77 interceptions to just 10 touchdowns.
Why does Alabama practice these plays every Thursday?
Even casual fans remember a few of the 10 that worked.
This article was written by Michael Casagrande from Alabama Media Group, Birmingham and was legally licensed through the NewsCred publisher network.