Ravell Call, Deseret News
Taysom Hill of the Brigham Young Cougars passes the ball against Boise during NCAA football in Boise, Thursday, Sept. 20, 2012.

PROVO — Suddenly, BYU has a quarterback quandary on its hands.

A year after Riley Nelson took over for ineffective starter Jake Heaps, could true freshman Taysom Hill be on the verge of replacing Nelson as the Cougars' new starter?

While Hill, who enrolled at BYU in January after serving an LDS Church mission, directed the Cougars' one and only touchdown drive in a 7-6 loss to No. 24 Boise State on Thursday night, coach Bronco Mendenhall said he expects an ailing Nelson to start Friday (6 p.m., MT, ESPN) against Hawaii.

"Riley is our quarterback. I love him. I want him to be healthy," Mendenhall said. "I want him to be able to look me in the eye and say, 'Coach, I'm absolutely ready.' I don't have any different feelings than I did going into this game. … There's no tougher person on the planet in my mind. He's a warrior. He won't come out unless you drag him out. I like him a lot."

Nelson is dealing with a significant back injury that is affecting his play. He completed only four of nine passes for 19 yards and three interceptions against the Broncos before he was replaced by Hill in the third quarter.

Hill had five series, with the first one ending abruptly after one play on a Michael Alisa fumble. But on his final drive, he marched the Cougars 95 yards on 11 plays, including a four-yard touchdown run with 3:37 remaining. Hill rushed for 39 yards on that drive.

Is it time to go with the freshman QB?

"I don't know that we have a decision to make," offensive coordinator Brandon Doman told BYUtv after the game. "It's all dependent upon Riley's health, and whether or not he can play like he's capable of playing. If he can't play Riley Nelson football, we'll have to go with an alternative plan. I'm not worried about those decisions. I just want to get him healthy. Ultimately, whether it's Riley or Taysom playing, we can't make the mistakes we're making."

Indeed, the Cougar offense has self-destructed and has been its own worst enemy at times this season. A bad quarterback-center exchange that resulted in a defensive touchdown was the difference in BYU's 24-21 loss to Utah, and Boise State's only TD came as a result of a pick-six in the third quarter. BYU had five turnovers against the Broncos.

"We might start winning some football games in tough environments if the offense would just stop giving the other team points," Doman said. "We've done it two weeks in a row. The defense has done everything they needed to do to win the game. The offense hasn't done our part."

After Nelson started off the second half with two straight turnovers, the coaching staff put Hill into the game.

"We realized that (Nelson) wasn't going to be able to give everything that we needed him to give us," Doman said. "So we made the change."

"It just didn't appear like (Nelson) was quite as sharp and feeling quite as good as we were hoping he would," Mendenhall said. "It was time to try to see if we could gather some momentum. It worked. Taysom came in and sparked us for the one drive we had and gave us a great chance right at the end to get a two-point play."

Doman said that Nelson is "hurt bad. He's fighting through an injury that's significant. He's probably one of the toughest human beings I've ever known."

Asked about potentially being the starter, Hill replied, "Obviously, I want to play. That's the competitive nature in me. Ultimately, that's up to the coaches. We'll just get ready and prepare for our next game."

Due to Nelson's injury, Hill said he got more reps in practice last week. Last Monday, the coaching staff decided to move Hill from No. 3 on the depth chart to No. 2, ahead of senior James Lark.

Hill, who completed four of 10 passes for 42 yards and rushed for 72 yards against Boise State, said that Nelson was supportive of him in the second half.

"Riley wanted to win that game just as bad as anybody else, whether it was him on the field or whether it was me. He's a senior, and ever since I came here in January, he's taken me under his wing. I've had the opportunity to learn from him. That didn't stop when I was able to go in and play. He's a great mentor. We were on the one-yard line and he's in there encouraging me and doing things to help me be successful."

What was Doman's assessment of Hill's play?

"There wasn't a football player on the field that played as hard as No. 4 did tonight," he said. "We're lucky to have him."