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Ravell Call, Deseret News
Riley Nelson (13) of the Brigham Young Cougars is brought down by Demarcus Lawrence (8) of the Boise State Broncos during NCAA football in Boise, Thursday, Sept. 20, 2012.

BOISE — BYU doesn't make quarterback changes easily. Never has.

What you saw Thursday night on national TV was BYU trying very hard to deal with its own monster as Bronco Mendenhall's defense put on a show for the ages.

Boise State 7, BYU 6.

It took three weeks of gutty appearances by Riley Nelson in games at Utah and here against ranked Boise State to pull the trigger since the senior injured his back in the Weber State game 13 days prior.

That either signaled that his coach Brandon Doman struggled to bench Nelson because, like a DieHard battery, he kept popping up in practices and begged to go, or he didn't want to run his offense with his second quarterback against the Utes and Broncos on the road.

On Monday, Doman called in No. 2 quarterback James Lark and told him he would now be third, he was moving up freshman Taysom Hill to No. 2. The future was now. Then, after considering all options, he started the veteran Nelson.

That he stayed with Nelson too long against BSU will be a water cooler debate for all time in Cougarville. Four of BYU's five turnovers came with Nelson at the helm.

It was a short week, only two practices. Tough to prepare Hill. Nelson's experience won out.

The result was hard to look at.

Thursday was BYU's worst offensive showing since the 2003 snow game against Utah in Provo.

It was painfully ugly.

BYU's defense looked Top Ten, at least up to its No. 9 ranking.

The offense looked like somebody should lose their job.

Nelson and his counterpart, Boise State's Joe Southwick, couldn't mount any kind of scoring drives in the game. It was like watching a pair of boxers will pillow gloves, duking it out to a draw.

Then, after playing most of the first half, apparent to everyone in the stadium and on ESPN that BYU could not pass the ball, it happened. Nelson tried to throw a touchdown pass to Cody Hoffman and it was woefully underthrown and intercepted.

In the second half, Riley got chased down by BSU's best defensive athlete, a defensive end named Demarcus Lawrence as he ran parallel to the line of scrimmage, picking up and putting down his cleats as fast as he could. He fumbled. Turnover No. 2.

After BYU's defense absorbed Boise State's attack for the millionth time, the dam broke for Nelson and Doman. Nelson threw a pick-six to give Boise State a third-quarter 7-0 lead. Turnover No. 3.

Still Nelson remained in the game.

Nelson's fourth and final turnover took place when he forced a high ball to JD Falslev, who tipped the ball high and into the hands of Jeremy Ioane.

That did it.

Doman decided Nelson, with all his leadership qualities, all his experience, all his guttiness, courage and desire to play with an injury, was not as good as a freshman with little experience but a healthy and ready body.

Hill, a high school star from Idaho, never had a chance.

His first two possesions of the game started at his own 1, his feet in BYU's own end zone. His first series ended in a Michael Alisa fumble at BYU's 1.

Still, Boise State failed to make BYU's offense pay as Ziggy Ansah, Brandon Ogletree and Daniel Sorensen made huge plays.

Hill's possessions started on the 1, 1, 26, 16 and 5.

On the road? A nightmare.

Still, in the waning moments, Hill led the Cougar offense the length of the field to where he faced a fourth-and-3 at BSU's 18. After a BYU timeout, 4:50 left in the game, Bronco fans in that end zone screaming like a tornado, BSU coach Chris Petersen waited to see BYU's formation — a classic spread formation — and called a timeout.

The kid hit Hoffman on a quick slant for a first down, good for 6 yards and a first down at the 12.

He then kept a bootleg play, churned his 4.5 speed into an 8-yard gain to the BSU 4.

Then he looked for a pass just long enough to keep BSU's linebackers in position and ran for a touchdown.

BYU went for a two-point conversion and J.C. Percy knocked Hill's pass down before it could get to Hoffman. BSU 7, BYU 6, 3:37 left in the game.

Hill had driven BYU 95 yards, more total yardage than the Cougars had gained in three quarters of the entire game. He finished as BYU's leading rusher with 72 yards, a touchdown, 4 of 10 passing.

Hill had a chance, when given the chance, to deliver a win for BYU in a place visitors hardly ever win.

This, you could say, was the anatomy of a decision.

A quarterback decision.

Decisions BYU doesn't make easily, quickly or according to Hoyle.

Email: dharmon@desnews.com TWITTER: Harmonwrites