Provo • Almost one month after he last took the field at LaVell Edwards Stadium, BYU quarterback Tanner Mangum started Friday night’s game wonderfully.

Two years after producing a dramatic victory over his hometown school, though, Mangum and the Cougar offense couldn’t sustain much of anything against Boise State. The Cougars scored a touchdown on their opening drive for the first time this season, then regressed by going scoreless over the last 53 minutes of a 24-7 loss.

The punctuation of another frustrating night came early in the fourth quarter, when offensive coordinator Ty Detmer called a long pass on a fourth-and-1 play near midfield. Mangum missed Jonah Trinnaman, who was well covered. Mangum went 18 of 33 for 164 yards with two interceptions, before freshman Joe Critchlow finished the game.

BYU coach Kalani Sitake explained the move as a case of “trying to find some momentum … trying to get a spark going.”

Sitake criticized Mangum for “making bad reads and, obviously, the interceptions didn’t help,” he said. “I’m not going to really sugarcoat it. Just not good enough.”

Mangum didn’t disagree. “A lot of that falls on me,” he said, citing some specific incompletions. BYU’s offense totaled 238 yards, slightly below the Cougars’ season average.

So the Cougars have suffered a fifth straight defeat in the same season for the first time since 1970 — with a sixth loss likely to come next Saturday at Mississippi State. That’s why a breakthrough against Boise State would have been very meaningful after BYU’s miserable September.

During a third-quarter timeout, the P.A. System played Earth, Wind & Fire’s “September” as DanceCam inspiration. That month is not a good memory around here. October hardly looks any better so far.

Mangum came back after missing two games (with an off week in between) due to an ankle injury and looked sharp at the start. The problem was his initial effectiveness translated into only seven points, as the Cougars remained stuck on that number for a long time.

The QB was erratic in the middle two quarters and BYU’s offense strained to piece together drives. Evidence of the struggles was Mangum’s topping 100 passing yards only in the fourth quarter.

Mangum’s injury occurred on the last play of a 19-13 loss to Utah on Sept. 9. On the second Saturday of September 2015, his touchdown pass on a fourth-down play in the final minute sent the Cougars ahead of Boise State and extended the remarkable start of his college career. He had thrown a game-winning TD pass on the last play at Nebraska the previous week.

But nothing like either of those moments happenedFriday, when BYU’s offensive and defensive players let each other down in the second half.

The late-night kickoff came after another week of quarterbacking intrigue in Provo. Mangum was expected to miss four to six weeks with his ankle injury and Friday fell just short of the four-week mark. His return became even more vital when backup Beau Hoge sustained a concussion in the second quarter of last week’s loss at Utah State.

Hoge exited just when he was playing well, throwing two touchdown passes — mixed with an interception that was returned for a TD — and running effectively on zone-read plays. The Cougars turned to Koy Detmer Jr., whose erratic passing resulted in three interceptions as USU gradually took control of the game.

Friday’s theme was somewhat the same, without the QB injury part. BYU’s offense enjoyed some productive moments in the first half, as Mangum completed 8 of his first 9 passes. Tight end Matt Bushman (seven catches) re-established himself as a primary target, after having been mostly ignored by Hoge and Detmer in the two games Mangum missed.

But the Cougars couldn’t finish a promising drive early in the second quarter, and then the offense struggled for long stretches. Boise State turned an interception of Mangum into a go-ahead field goal. After the Cougars’ three-and-out sequence, the Broncos drove 74 yards for a touchdown and a 17-7 halftime lead.

BYU recorded only 115 total yards in the first half, with Mangum going 8 of 13 for 68 yards. He added only 27 yards on the Cougars’ two possessions in the third quarter, and a mild fourth-quarter rally was inadequate after Boise State took a 24-7 lead.

“We need to develop an identity,” Sitake said. “I know that sounds crazy, midseason.”

Sitake pointed to freshman running back Ula Tolutau as the possible solution to that issue. Tolutau gained 38 yards on nine carries, including a 3-yard touchdown, but BYU went away from him after Boise State surged ahead and the Cougars had to use their passing-oriented personnel.

So here were the Cougars, coming off a September when they lost all four games, including blowouts by LSU and Wisconsin and two in-state defeats. And considering BYU needs seven wins for bowl eligibility in a 13-game season, the math was not looking favorable.

The outlook worsened after Boise State’s win. This comparison will hurt even more: Robert Anae’s Virginia offense posted 42 points and 400-plus yards as of early in the fourth quarter in Boise two weeks ago, as former BYU coach Bronco Mendenhall’s staff and players delivered a convincing victory over the Broncos.

BYU’s fifth straight loss left Sitake searching, again. “I just want to go to work and get it fixed,” he said.

That project might take more than another week.