Boise State is beginning to develop the 1-2 punch in the running game that has been a staple of the offense under coach Chris Petersen.

Redshirt freshman tailback Jay Ajayi continued his week-by-week emergence Saturday with 91 rushing yards in the 20-10 defeat of Fresno State.

Ajayi carried a career-high 15 times. He got the ball six times against New Mexico and nine times against Southern Miss in the previous two games.

And against Fresno State, he was trusted to take the ball as the Broncos ran out the clock in the fourth quarter.

“You have to have a 1-2 punch,” Petersen said. “You’re not going to have the type of running game we want to have if you don’t.”

The Broncos began the season with senior starter D.J. Harper, senior Drew Wright and a host of freshmen. Wright has missed three straight games with an injury and hasn’t been much of a factor.

That created an opening for Ajayi or true freshman Jack Fields to carve out a niche — and Ajayi, a 222-pound, tackle-breaking alternative to the elusive Harper, has done just that.

Ajayi has 251 yards on 31 carries — an average of 8.1 yards per carry.

He tore an anterior cruciate ligament in practice last season and was suspended for the opener against Michigan State.

“We’ve always known he’s a great player,” said Harper, who rushed for 122 yards. “It’s really good for him to come back from what he’s been through. It’s exciting to see him out there playing well. That helps me out a lot.”

The Broncos rushed for 215 yards — their third 200-yard game of the year.

“Those two guys are great,” quarterback Joe Southwick said. “I love that they’re in my backfield. If that O-line keeps blocking like that, and we keep running like that, we’ll get some things done.”

Chadd Cripe: 377-6398