Josh Rosen vs. Tanner Mangum four-round scoreboard

Saturday night's matchup featured two of the most exciting emerging talents in college football, led by two true freshmen: UCLA's Josh Rosen and BYU's Tanner Mangum.

BYU came into the match hoping to secure their first Top Ten victory since 2009; their all-time record in road games vs. AP top ten opponents was 1-12 heading into the match.

Much like we did here at for the NFL season-opener last week for Tennessee's Marcus Mariota vs. Tampa Bay's Jameis Winston, we're breaking it down boxing-style for you.

Round one: Mangum over Rosen 10-9

Score: BYU 7, UCLA 3

Rosen: 2-of-6 for 21 yards, zero touchdowns and one interception

Mangum: 8-for-13 for 58 yards, zero touchdowns and zero interceptions

Rosen went three-and-out to start the game; Mangum's BYU offense drove 71 plays for a touchdown. That set the pace early for BYU.

When UCLA got the ball back, UCLA drove 83 yards -- Rosen was eventually picked by BYU's linebacker Harvey Langi. But Mangum, too, showed his football mortality and was sacked on the next drive.

Both Mangum and Rosen would exchange three-and-out possessions in an otherwise uneventful quarter.

UCLA was shutout during the first, but the scoring deficit didn't punish UCLA as much as it could have. Perhaps the most important takeaway of the first quarter: Rosen finally looked like a true freshman, offering a necessarily humbling experience in Pasadena.

Round Two: Mangum over Rosen 10-7

Score: BYU 10, UCLA 3

Rosen: 3-for-9 for 31 yards, zero touchdowns and two interceptions

Mangum: 6-for-10 for 43 yards, zero touchdowns and zero interceptions

Rosen was 2-of-9 to start the game, completing as many throws to his own team as he did to Landi. BYU responded with a field goal, earning Mangum a 10-3 lead.

Once UCLA got the ball back, on third-and-ten in the second quarter, Rosen nearly threw his third interception of the night before UCLA's special teams unit came out to punt.

Later in the second quarter, after a BYU fourth-down conversation, Mangum was sacked for the fourth time of the night. Challenged for his second fourth-down conversion of the drive, Mangum came up short.

But UCLA wasn't able to capitalize. Was Rosen playing hurt? It seemed such, when he hit Kai Nacua for his third interception of the first two quarters. He was 5-of-15 for 52 yards with three picks to end the first half.

Rosen, who threw picks in the second quarter, once again came up short in his "boxing round" against Tanner Mangum.

Round Three: Mangum over Rosen 10-9

Score: BYU 17, UCLA 10

Rosen: 3-for-5 for 21 yards, zero touchdowns and zero interceptions

Mangum: 8-for-8 for 71 yards, one touchdown and zero interceptions

Through three quarters, Mangum was sacked five times. Otherwise, however, he looked nearly flawless.

Meanwhile, UCLA shied away from the air attack and instead relied on rusher Paul Perkins to even up the score. During the third quarter, Rosen managed not to allow a turnover. But he only had five passing attempts; UCLA totaled 41 yards on the ground compared to 21 in the air.

Mangum also continued his dominance while throwing off his back foot, looking sharp as ever during a dominant effort in the third. He met Mitch Matthews for a 14-yard touchdown pass, giving BYU another lead.

By relying on Rosen less during the third quarter, he made fewer mistakes. For BYU, it was all Mangum everything.

The BYU freshman quarterback was sacked, hit and hurried all game by UCLA. But Mangum remained competitive, showcasing some of his best throws of the season.

Round Four: Rosen 10, Mangum 8

Score: UCLA 24, BYU 23

Rosen: 3-for-3 for 33 yards, one touchdown and no interceptions

Mangum: 8-for-16 for 72 yards, zero touchdowns and one interception

Early in the fourth quarter, around a minute after BYU's field goal to open the quarter, Rosen met receiver Jordan Payton for a 20-yard touchdown. It was a perfect throw.

The impressive confidence from the true freshman was mostly significant because it showed how he performs under pressure. Rather than come into the fourth quarter showing jitters and nerves, Rosen looked mature and like he'd been there before. In an otherwise rocky effort from the UCLA quarterback, it wasn't all bad news.

Though BYU scored another field goal, the Bruins were once again saved by their rushing attack. This time, it was backup running back Nate Starks who led UCLA's touchdown drive. Rosen wasn't asked for much, but didn't make any mistakes either.

Perkins ended the game with 219 yards on 19 carries; Starks ended with 81 yards on 7 carries.

With 3:18 remaining in the game, BYU's Mangum was tasked with another series of late-game heroics.

Scrambling in the pocket, with all the pressure in the world on his shoulders, Mangum completed consecutive passes. Though inexperienced, he appeared like he'd been there before. He looked down field for the open man and a took a draw when there was none.

But with 1:09 remaining in the game and on a fourth down effort, Mangum threw his first pick of the game. It was UCLA's defensive star Myles Jack, not either of the quarterback, who came out with the most important play of the game.

Mangum was unable to earn a victory during an otherwise great game for BYU. But he took the QB boxing match, ending the game 30-of-47 for 244 yards, one touchdown and one interception.

Rosen had a less-than-great game. He was 11-for-23 for 106 yards, with one touchdown and three interceptions.

Final: Mangum 38, Rosen 35

Bryan Kalbrosky is the Pac-12 South producer for FOX Sports. Follow him on Twitter by clicking below. Follow @BryanKalbrosky