LAS VEGAS — For most of three quarters Saturday afternoon, BYU outplayed Utah at the Royal Purple Las Vegas Bowl.

But the Utes capitalized on a nightmarish start for the Cougars — five turnovers on BYU’s first five possessions, including pick sixes by bowl MVP Tevin Carter and Dominque Hatfield — and then staved off a furious BYU comeback to earn a 35-28 victory before a sellout crowd of 42,213 at Sam Boyd Stadium.

With 4:38 remaining in the first quarter, Utah was royally smashing royal blue-clad BYU in the Royal Purple Las Vegas Bowl, 35-0.

It was such a stunning opening of the game that nobody, including Ute coach Kyle Whittingham, knew exactly what was going on.

“It was like the Oregon game, but intensified, like a game on steroids,” he said, adding that his defense forced BYU into those miscues. “We made those plays. Those (turnovers) weren’t gift-wrapped."

The Cougars rallied to score 28 unanswered points and furnished yet another dramatic finish in the rivalry game (15 of the last 18 rivalry games have been decided by seven points or less), but their comeback attempt fell short.

“Not sure I've been more proud of my team,” said coach Bronco Mendenhall. “They stayed together and unified and battled back and made it a great football game. … That was a really good game and remarkable comeback. Utah hung on, to their credit.”

“That game was the strangest game I think I’ve ever seen,” said BYU athletic director Tom Holmoe.

Whittingham said his team got “complacent” after a five-touchdown lead.

“It was a good win for our program,” he said. “We started off and played real well the first quarter, very average in the second quarter, then pathetic in the third quarter and half of the fourth quarter, then finished off pretty average. So, you add it up and evaluate it as a whole, the entire body of work wasn’t bad.”

BYU quarterback Tanner Mangum, who completed 25 of 56 passes for 315 yards, two touchdowns and three interceptions, scored on a 4-yard run with 3:23 to turn it into a one-possession game.

Mendenhall debated with his staff whether or not to go for an on-side kick before deciding to kick the ball deep. The result was a kick that went out of bounds, giving Utah the ball at the 35-yard line.

The Utes picked up a couple of crucial first-down runs in the final few minutes by Joe Williams to seal the victory.

“The main focus was just to get a first down,” said Williams, who ran for 91 yards and two touchdowns on 25 carries. “We huddled up and talked about it as an offense. 'Two more first downs and this game is ours.’”

While the Cougars (9-4) outgained the Utes (10-3) in total offense, 386-197, one stat told the ultimate story: BYU had five turnovers and Utah had zero.

With the win, the Utes extended their winning streak against the Cougars to five games and denied Mendenhall his 100th career victory in his final contest as the Cougar coach before he moves on to Virginia.

Whittingham, meanwhile, improved to 9-1 in bowl games and claimed the best bowl win percentage in NCAA history.

Amid reports that Kalani Sitake would be the new coach at BYU prior to kickoff, the Cougars looked unprepared and mistake-prone from the outset.

BYU entered Saturday’s game as one of the best teams in the nation in ball security, with 15 turnovers in 12 games. Against Utah, the Cougars imploded, with a Mangum fumble on BYU’s first possession, followed by a 28-yard pick six by Carter, another interception by Carter, a 46-yard interception return by Hatfield and a fumble by Squally Canada, in his first carry in a Cougar uniform.

BYU's comeback started with a 97-yard drive at end of the first half, with a 3-yard touchdown pass from Mangum to Remington Peck with 36 seconds left before halftime. The Cougars scored another TD in the third quarter and two more in the fourth.

“It was game on when it went to 35-21,” Whittingham said. “We had enough in the tank to get the win.”

Despite overwhelming adversity early on, BYU was determined to keep playing hard.

“A lot of credit goes to the way we’re coached. Quitting is not an option,” Peck said. “There was no doubt in the locker room that we were going to come out and fight.”

“No matter what happens or how much we get down by, this team will fight back,” said BYU defensive lineman Bronson Kaufusi.

“You have to credit (BYU) for hanging in there and fighting back,” Whittingham said. “They have a lot of resiliency and heart, and we saw that today.”

EMAIL: jeffc@deseretnews.com