POCATELLO — For most of the day, Montana was making the little mistakes that were bound to cost them.

When the game was on the line, the Grizzlies reversed course. Idaho State made the fatal errors and was outscored 26-10 after halftime in Saturday’s 39-31 loss at Holt Arena.

Montana (4-2, 2-1 Big Sky Conference) left points on the board with a missed field goal, blocked extra point and a pair of failed two-point conversions. Penalties stopped offensive drives and extended the Bengals’. But the league’s top offense wouldn’t be slowed for long, and built an 11-point lead with 6 minutes, 38 seconds to play in the final quarter.

Meanwhile, Idaho State (3-3, 1-2 Big Sky) self-destructed after heading into halftime with a 21-13 lead and minimal errors. The defense fell suspect to big plays while the offense suffered critical dropped passes and penalties late in the game.

Bengals coach Rob Phenicie said as much in his first few words of the postgame press conference.

“Had too many dropped passes, too many sacks, too many penalties and turnovers,” he said. “That’s our formula. If you don’t have those, you win games. If you have those, you don’t come out ahead.”

The Bengals’ final drive began with an 11-point deficit and 2:49 to play. On the prior possession, a tipped pass intended for Michael Dean was nearly intercepted, Mitch Gueller dropped a pass at his hands, and Austin Campbell was jarred for an incomplete pass.

On a gutsy fourth-down call, Bengals quarterback Tanner Gueller made a lateral pass to Mitch Gueller, who threw back across the field to Tanner.

The play went for eight yards and a first down, but an illegal block penalty on Chase Collins negated the gain and forced the Bengals to punt.

By the time ISU made its final push for points, the errors were too numerous to overcome. The Bengals cut the score to 39-31 with Parker Johnson’s 35-yard field goal and needed to recover an onside kick to have one last chance.

Johnson’s kick was nabbed by Montana’s Jeremy Calhoun, and the Griz kneeled out the clock.

It was a disappointing end given ISU’s promising start, and is a loss that’s sure to sting. A win against the winningest team in Big Sky history would have vanquished ISU’s critics. The loss will get lost in a sea of reasons to doubt the upstart Bengals.

“We definitely gave everything we had to win this game and put a lot into it,” Mitch Gueller said. “A lot of guys had a lot in this game, and it’s just tough to get a loss.”

Montana started its superb second half with a 35-yard touchdown pass from Gresch Jensen to Justin Calhoun early in the third quarter, and took the lead on Alijah Lee’s 1-yard run to close the frame. A 6-yard hookup from Jensen to Josh Horner gave the Griz their only two-score lead of the game with 6:38 to play.

After getting flagged six times in the first half, Montana committed one penalty the rest of the way. The defense sacked Tanner Gueller six times and forced ISU’s signal caller to scramble away from pressure on drive after drive. Gueller entered the game with a Big Sky-high 17 sacks and was harassed by the Griz’s aggressive defense.

Gueller netted 13 yards rushing, including a 21-yard keeper, on 16 carries. The six sacks cost him 64 yards.

In the first half, the Bengals outgained Montana 287-214 and limited the Griz to one play of over 20 yards. Tanner Gueller and Mitch Gueller hooked up for two touchdowns, and the Bengals scored in quick, typical ISU fashion.

After halftime, Montana’s offense opened it up. The Griz notched four plays of 35 yards or more and found the end zone on four consecutive drives in the third and fourth quarters. Montana finished with 519 yards of offense, averaged 7 yards per play and stayed perfect in the red zone this season by going 5 for 5.

The Grizzlies converted two third downs and one fourth down on the drive that put them ahead 39-28.

“We made a mistake, they capitalized on it,” Bengals linebacker Joe Martin said. “We need to step up and be perfect and not do that. That’s what Montana did today, and they came out with a W.”

Tanner Gueller completed 25 of 40 passes for 359 yards and three first-half touchdowns. His yardage total was three yards shy of his career high, and his 14.4 yards per completion put him at 15.5 yards per completion this season. Gueller entered the game ranked seventh in the FCS at 15.8 yards per completion.

Mitch Gueller set a career high with 188 yards on nine catches, including two touchdowns. The sophomore has grabbed 17 catches for 470 yards and six TDs since making his season debut two weeks ago at Northern Colorado.

Mitch also had three of ISU’s six dropped passes.

“I just think there’s a level of confidence with each other,” Phenicie said of the Gueller brothers. “It’s fun having that. Takes a little pressure off of (wide receiver Michael Dean). It’s a good thing to have.”

ISU’s rushing attack was led by James Madison’s 18 carries for 88 yards. Ty Flanagan played for the first time since leaving the Sept. 16 Nevada game with an injury and rushed 12 times for 55 yards and a 4-yard touchdown.

Mario Jenkins recorded his third double-digit tackle game of the season with a team-high 13. ISU’s redshirt senior captain briefly left the game with what looked to be an arm or hand injury with 4:39 left in the first quarter. He returned on the second pay of the second frame and played the rest of the way.

Phenicie said Jenkins was injured after Montana kicked an extra point following a first-quarter touchdown.

“They were being extremely dirty in the pile after the field goal,” Phenicie said. “I asked him if it happened afterwards, and he said, ‘Yeah.’ … Stuff went on, and they hurt him.”

The loss might sting most for Phenicie, who helped Montana reach three national title games in seven years as the team’s offensive coordinator. He felt his new team had something to prove to his old team — perhaps that he had something to prove in his first year as a head coach.

The teams don’t square off again until 2019. Phenicie and the Bengals trek on next week at Sacramento State.