True freshman quarterback Tanner Mangum found himself in Nebraska's Memorial Stadium with the game on the line. With all the poise of a seasoned veteran, Mangum found Mitch Mathews to cap an incredible 33-28 victory for the Cougars.
It was the greatest finish for BYU since Jim McMahon stunned SMU in the 1980 Holiday Bowl.
It's a bittersweet victory for the Cougars as Taysom Hill's season, and possibly his football career, is over. A few other key Cougars also fell to injuries in the season-opener.

Against all odds, the Cougars are coming home from Nebraska 1-0. Here's BYU's grades for the game.
Quarterback
It was a bittersweet game for BYU's quarterbacks. Hill had a solid day with 268 yards passing, 72 yards rushing and three touchdowns with one interception. However, Hill's season ends early for the third time as he breaks his foot. He might not take another snap in a BYU uniform.
Enter true freshman Tanner Mangum. A few short months ago, he was serving an LDS mission, not practicing football. It didn't matter as Mangum went 7-for-11 for 112 yards and the most incredible BYU Hail Mary since 1980. The Cougars will depend on this extraordinary true freshman for the rest of 2015.
Grade: A
Running backs
It wasn't a red-letter … er … blue-letter day for BYU's running backs. These backs needed to take the pressure off Hill, and unfortunately that didn't happen.
Adam Hine was the only BYU running back to get anything done as he made a critical first down in the Cougars' final drive. Algie Brown caught a couple of passes, but he dropped a vital fourth-down pass and took points off the board. Nate Carter lost 11 yards on the day. This position has a lot of work to do with Jamaal Williams out.
Grade: D
Wide receivers
BYU's wide receivers made big play after big play for the Cougars. Nick Kurtz had a phenomenal game with five catches for 123 yards. Not to be outdone, Mitch Mathews made both touchdown grabs, including the Hail Mary at the end. Terenn Houk, Devon Blackmon, Mitchell Juergens, Colby Pearson, Moroni Laulu-Pututau and Kurt Henderson all had grabs for the Cougars and provided plenty of highlights.
Grade: A+
Offensive line
On the one hand, the offensive line provided enough protection to both Hill and Mangum and handled Nebraska's pass rush well. On the other hand, the line struggled to open up lanes for running backs.
But here's one huge improvement over last season: The line didn't draw a single false start penalty and just two holding penalties. The Cougars averaged 81.0 penalty yards per game last season.
Grade: B
Front seven
BYU is going to miss Travis Tuiloma. The big defensive tackle was huge in stopping Nebraska's run game up until he left the game. However, Bronson Kaufusi had some solid plays, including a big sack, and Logan Taele added a sack of his own. Still, the Cougars struggled containing the run once Tuiloma went out. However, the line did do just enough to help the team win the game.
BYU missed starting linebacker Sione Takitaki, but the linebackers held their own. Converted running back Harvey Langi looked a little lost on some plays, but he did pick up a sack on the day. Fred Warner forced and recovered a fumble in Kyle Van Noy fashion.
Not a bad day for the BYU front seven, but giving up 126 yards rushing isn't worthy of an A.
Grade: B
Secondary
Nebraska went after the BYU secondary early and often, particularly with Kai Nacua out of this game. The Cougars gave up 319 yards through the air to the Cornhuskers. However, Micah Hannemann had the second most impressive play of the game with an incredible interception on the sideline.
Grade: C-
Special teams
The Cougars had one hiccup with a kickoff out of bounds, but special teams had a solid game. Trevor Samson was solid with two field goals from 35 and 42 yards. Johnny Linehan impressed with five punts for 255 yards, including a 77-yard bomb. Hannemann had a nice 11-yard punt return. No huge plays for special teams, but definitely a good day.
Grade: B+
Coaching
Credit Bronco Mendenhall and the coaching staff for making some adjustments to the defense after a tough first quarter. The coaches had the players ready in a tough season-opener at one of the most storied stadiums in college football. Also, this team held together as injures and momentum turned against BYU in the second half.
However, you have to take some points off for poor clock and timeout management. The Cougars burned two early timeouts in the second half that could have doomed BYU in this game.
Grade: B
Overall
While not a flawless victory, this win is one for the ages. BYU got the W and broke Nebraska's 29-game home-opener win streak. The Cougars have a lot to figure out as they lose Hill for the season and Tuiloma for 6-8 weeks. This is a key win as the Cougars continue their brutal September at home against Boise State next Saturday.
Grade: A-
Lafe Peavler is a staff sports writer for the Deseret News. Follow him on Twitter @LafePeavler.