BYU’s Hail Mary victory over Nebraska was one for the ages, but it was also a bittersweet feeling for the Cougars.

Taysom Hill suffered a season-ending Lisfranc injury that is cutting his season short for the third time in four years.

True freshman Tanner Mangum stepped in for Hill in a hostile environment engulfed in the loud Sea of Red, but Mangum displayed poise and confidence beyond his years, granted, those years are a tad bit higher than a typical true freshman as Mangum turns 22 on Tuesday.

Mangum stepped in for Hill after he went out early in the first half, and in his first few plays as a Cougar, made a nice throw and as the kids these days say, was low key shifty on the run. Hill then came back in and we all thought Mangum wouldn’t be seen from again, unless it was mop-up duty in a blowout game later in the schedule. Then of course, Hill went down again early in the fourth with the Cougars down by four.

To think of what Mangum pulled off is remarkable, and to do it in one of college football’s most storied venues makes it a fairy tale opening, and has Cougar fans chomping at the bit to see what’s next.

Related: BYU Defeats Nebraska 33-28 on Last-Second Hail Mary Touchdown Pass

Most programs would have no hope for success after losing a star like Hill. But after what we saw in one game from Mangum, the Cougars still have an opportunity to put together a season that ends with more than eight wins, the total they’ve had the past three years.

Mangum is now in charge of leading this BYU team, and will look to build on the positive momentum coming out of the improbable victory in Lincoln. But one question many folks around the country are probably now asking is, who is this Tanner Mangum kid? Well, time to get familiar.

Mangum hails from the same state as Hill, the Gem State, Idaho. Mangum was a heralded recruit, considered the third-ranked quarterback in the country in the class of 2012 per Rivals. To understand how lofty Mangum’s recruiting status was, he was the co-MVP of the Elite 11 in the 2012 class with a guy you might remember, former Heisman Trophy winner Jameis Winston. Not bad company to be associated with I’d say.

With those impressive accolades, folks that follow BYU football closely have always been excited about the future prospects of the program with Mangum lining up as the Cougars’ signal-caller, they just didn’t want or expect this era to take center stage so soon. But now that it is here, folks are buzzing about the potential this guy has.

Hill was known as a dual-threat quarterback. He made significant strides as a passer, but where he made a name for himself was his elite running ability. Mangum doesn’t have many similarities when you compare him side-by-side to Hill. To describe Mangum’s style of play, think of BYU quarterbacks from yesteryear during the Air Edwards era. Or if you want a more recent comparison, look at Max Hall. These were all classic drop-back quarterbacks that can throw the football with precision and accuracy, and if needed, can pick up a first down on the ground with their legs in a pinch. That’s Mangum.

Mangum is nowhere near Hill’s level in terms of athleticism, and he would even tell you that. During a “SportsCenter” appearance on Sunday, Mangum said, “I don’t run a 4.4 40, but I’ll work hard, and I feel like I’m a student of the game.” That type of attitude from Mangum is one of the reasons head coach Bronco Mendenhall had such high praise for Tanner during fall camp last month. In fact, it wasn’t just praise, it was love. “Love, love, love, love, continued loves, Tanner Mangum.” That was the exact quote from Mendenhall after seeing Mangum through two practices in camp.

What makes this Hail Mary and story even more remarkable, is that less than 100 days ago, Mangum was serving a mission for the Church of Jesus Christ of Latter-day Saints in the country of Chile. On LDS missions, players don’t train or use the time to mature physically. These missionaries only have 30 minutes to exercise in the mornings, that’s pretty much it when it comes to physical conditioning. Everything else done out on the mission field revolves around your commitments as an LDS missionary. Mangum himself said, he only threw a football a few times during his mission with some of the locals in Chile, but no conditioning or training like most high-level FBS athletes are engaged in during the offseason.

It’s difficult for returning missionaries that are also student-athletes to come back to perform at a high level right away, but Mangum has worked his tail off since he came home on June 3. Knowing that he had a great opportunity to take over as the second-string quarterback behind a starter who had suffered two season-ending injuries in the past, Mangum was preparing like he was atop the depth chart by studying relentlessly in the film room and preparing himself physically for when his number would be called.

Now that his number his been called, Mangum has already been elevated to star status in Provo. So how will he follow this up?

The Cougars will face Mangum’s hometown team, Boise State this Saturday in Provo, then a pair of road games with UCLA and Michigan. That was expected to be a tough stretch for a seasoned senior in Hill, so for a true freshman like Mangum, the odds of BYU coming out on the winning end of those games is probably not in its favor at this point. But hey, the odds weren’t in BYU’s favor when there was just one second left in regulation in Lincoln either.

It’ll be interesting to see where offensive coordinator Robert Anae steers this offense under Mangum. Do the Cougars go back to an Air Raid-style of offense, similar to Texas Tech from the Mike Leach days? Anae was an offensive line coach at Tech under Leach, and incorporated the pass-heavy attack at BYU in 2005 for the first month of the season. It’s an offense that might need to be considered because BYU’s running backs without Jamaal Williams after week one are nothing to write home about at the moment.

BYU will need to win games with Mangum’s arm. Luckily for the new starting quarterback, he has a talented receiving group to throw to that goes eight deep, and boasts a trio of wideouts that stand 6-foot-5 or taller in Mathews, Nick Kurtz, and Terenn Houk.

We will have a great idea of how this offense will look after Saturday night’s showdown with Boise State, but regardless of how the offense is executed the Cougars still have a bright future with this polished and poised man that has been training his whole life to become BYU’s next great quarterback.

— Written by Mitch Harper, who is part of the Athlon Contributor Network. Harper is the BYU reporter and insider for 1320 KFAN and co-host of "The Cougar Center" podcast. Follow him on Twitter @Mitch_Harper.