Tom Smart, Deseret News
Brigham Young Cougars quarterback Riley Nelson (13) during pre-game as BYU plays Idaho in the Cougar's final home football game on 2012 Saturday, Nov. 10, 2012,in Provo, Utah.

SAN DIEGO — With senior quarterback Riley Nelson at the controls, BYU entered the 2012 season with high expectations.

But Nelson suffered a major back injury in the second game, and then the Cougars later turned to a true freshman, Taysom Hill, before he sustained a season-ending knee injury.

Nelson eventually returned, but a rib injury against San Jose State sidelined him again.

As BYU concludes a turbulent season with an appearance in the Poinsettia Bowl on Thursday (6 p.m., MT, ESPN) at Qualcomm Stadium against San Diego State, it appears James Lark will get the start — although nothing has been announced officially.

Coach Bronco Mendenhall could be relying heavily on another senior, Lark, to help his team cap the year with a victory.

Lack of continuity at quarterback has certainly played a role in this season's offensive struggles. "It's kind of prevented us from having the marquee season that we were hoping for, if you gauge it by wins and losses," Mendenhall said.

The coach has hinted that both Lark and Nelson could play against the Aztecs.

Lark threw for 384 yards, six touchdowns — and zero turnovers — in his first career start in the regular-season finale at New Mexico State. Mendenhall said he's always had confidence in Lark's abilities.

"One game doesn't necessarily change my opinion much. The quality of opponent in that game, while New Mexico State wasn't a strong football team, his performance was very good," the coach said. "He's the healthier of the two quarterbacks right now. He's taken more reps (in practice) than Riley. That doesn't mean that both won't play. I've always thought James was capable, and hopeful that he'll be able to demonstrate that (in the bowl game)."

The Cougars have dropped four games by a total of 13 points. A handful of plays — particularly turnovers — have doomed BYU in its five losses.

Mendenhall mentioned that his team owns a 56-6 record in his eight seasons in games when it has fewer turnovers, or the same amount of turnovers, as the opposition.

"If we don't turn it over, and are at least even with our opponent, we have a great chance to win," Mendenhall said. "This year, we've turned the ball over more than we've normally done and we've still had a great chance to win. One less turnover here or there is really the difference in the season ... So we're trying to help our team understand that they just have to play within their job description, that would be at quarterback and any other spot. That gives us our best chance (to win)."

Yes, turnovers could determine the outcome in the Poinsettia Bowl.

Meanwhile, the roles have reversed for Lark and Nelson. While Nelson once received the majority of reps during practice, Lark has been doing that the last couple of weeks. But there's a strong possibility that both senior quarterbacks — in their final collegiate game — will see action Thursday.

At least, that's what SDSU coach Rocky Long is expecting.

"I've been saying for two weeks that he's going to play both quarterbacks," Long said at Wednesday's Poinsettia bowl press conference.

Then he turned to Mendenhall, and said, "Can you tell me now?"

"I like to build intrigue," Mendenhall quipped. "It's good for ratings."

BYU's QB situation should keep Long, who is also SDSU's defensive coordinator, on his toes.

"One's right-handed and one's left-handed. So when you see the left-handed quarterback (Nelson) go in, some of our blitzes come from our right side," Long said. "When it's the right-handed quarterback (Lark), the blitzes come from the other side. The dingbat that's calling the defense had better understand that, which happens to be me. You can't have a different game plan for both because there's not enough time for that."

Mendenhall said he's "not a big fan" of a two-quarterback system, "but based on how Rocky's defense is playing, if there are scramble lanes and we can run a little bit, then obviously that's more suited to a running quarterback. If their coverage is struggling, it might be more suited to the other. There possibly could be a change based on how the game is going. I reserve the right to do that."

For BYU true freshman running back Jamaal Williams, it doesn't matter which quarterback is in the game.

"We feel comfortable with both quarterbacks," he said. "We know we can put 100 percent trust in both of them, because we know they're both going to come out and do the best they can to help us win the game."

While BYU's defense, ranked No. 3 in the country in total defense, has kept the Cougars in games all season long, it's interesting to note that under Mendenhall, BYU is 65-8 when allowing fewer than 24 points in a game. Trouble is, four of those eight losses have come this season, due to an offense that has been punchless at times.

The defense would love nothing more than to finish the season with another memorable performance.

"We've talked about that. We want to go out with a bang," said senior linebacker Brandon Ogletree. "We've had a great year. It would be a shame to go out with anything less than our best. We definitely want to put an exclamation point on our body of work. I think we will."

Offensively, BYU is hoping to channel its many memorable performances from Holiday Bowls past in San Diego on Thursday night with either Lark or Nelson. Or both.

"We're anxious to finish on a high note," Mendenhall said.