The Boise State Broncos were a one-phase football team Thursday night at Bronco Stadium.

That phase — a dominant, big-play defense — was good enough to beat BYU.

It wasn’t enough to please coach Chris Petersen — or a grumbling fan base.

No. 24 Boise State defeated BYU 7-6 with a defense that scored the Broncos’ only touchdown, forced five turnovers, stopped a two-point conversion with the game on the line and allowed just 200 yards.

The offense failed to score a touchdown for the second time in three games. The special teams didn’t help, either, with a failed fake punt, a missed field goal and kicking woes so bad that Petersen four times left his offense on the field rather than try for three points.

“How ’bout that defense?” Petersen said to open his press conference. “Unbelievable. Unbelievable. … Trust me, I’ve got the same feeling that probably everybody has — it’s the weirdest feeling. I’m so ecstatic for that one side, and we’ve definitely got to go back to the drawing board on the other side.”

The defense played with a relentless passion from the first snap (a sack) to the last (the two-point play) — fueled by a record crowd of 36,864 that was so loud that players’ ears were hurting.

The group made up for an offense that was shut out at home for the first time since joining the Football Bowl Subdivision in 1996, according to ESPN research.

“That’s the best defensive performance I think I’ve ever seen,” senior linebacker J.C. Percy said.

The defense forced two turnovers in the first half — an interception by senior cornerback Jamar Taylor near the Broncos’ goal line and a fumble forced by Taylor near midfield.

The group delivered again on the opening drive of the second half.

On third-and-6, Boise State sent two blitzers from BYU quarterback Riley Nelson’s left. Senior defensive tackle Mike Atkinson ran a stunt, which required him to loop behind the other rushers to the outside.

He looked at Nelson and saw him prepare to throw. Atkinson reached into the air, snagged the football and darted toward the end zone. The former high school fullback — he has played the position at Boise State occasionally, too — used a lead block from defensive end Demarcus Lawrence to rumble 36 yards for the TD.

“You usually don’t see a refrigerator who’s 310 pounds who can move like that,” Petersen said.

The defense forced two more turnovers, including a fumble the Broncos recovered on the Cougars’ 1-yard line, but couldn’t sustain anything on offense.

After the fumble, senior tailback D.J. Harper lost a yard twice and regained those 2 yards on a lateral. The Broncos were a foot from the goal line and called a quarterback sneak, but junior Joe Southwick couldn’t fight his way in.

That bought time for the Cougars. They benched Nelson in favor of true freshman quarterback Taysom Hill, the speedy Highland High graduate. Hill finally got the offense moving midway through the fourth quarter and led an 11-play, 95-yard touchdown drive.

He bulled his way into the end zone on a 4-yard run with 3:37 left to make the score 7-6.

“He’s a heck of an athlete,” Petersen said. “He’s fast. He’s strong, too. He pulled us into the zone.”

BYU coach Bronco Mendenhall, like TCU’s Gary Patterson last year, decided to try a two-point conversion. TCU upset Boise State 36-35 by converting its play.

Hill took the snap and Atkinson immediately forced him out of the pocket. Hill rolled to his right and threw toward a receiver in the corner of the end zone.

Percy jumped in front of the pass and knocked it down.

“It was sure neat to be able to finish off the night that way,” Percy said. “It was a spectacular night.”

Said Mendenhall: “I wanted to win. We had momentum for the first time in the game, moving the ball offensively. We wanted to capitalize on it. I’d do it again.”

BYU had used all its timeouts, so Boise State only needed one first down to run out the clock. Southwick hit tight end Holden Huff for 15 yards to secure the victory.

It was a rare highlight for an offense that managed just 261 yards against a BYU defense that has held 10 straight opponents to fewer than 300 yards.

Harper rushed for 112 yards, nearly matching Southwick’s output. The quarterback was 15-of-25 for 145 yards.

“We definitely expected (the Cougars) to be good,” Petersen said. “To shut us out, I don’t think we were expecting that.”

The Broncos had not failed to score an offensive touchdown in a game since Petersen joined the staff as offensive coordinator in 2001 before the opener against Michigan State, a 17-13 loss that also included a defensive TD.

Now it’s happened twice.

There is heat on Southwick, whom Petersen said he didn’t consider benching, and first-year offensive coordinator Robert Prince.

But Southwick and sophomore receiver Matt Miller said the offense isn’t as far away as it looked Thursday. The group generated 599 yards Saturday against Miami (Ohio).

“We had some good (plays),” Southwick said. “We’re close, man. But again, if we want to be a good offense, we have to finish and that starts with me.”

Petersen said the coaches will work to simplify the offense. They also will spend some quality time working on red-zone and goal-line plays.

“We shot ourselves in the foot a few times on offense,” Southwick said, “but our defense carried the flag today and kicked some serious butt. I’m really proud of those guys.”

Chadd Cripe: 377-6398, Twitter: @IDS_BroncoBeat