FRESNO — Valley Children’s Stadium is constructed as a bowl, with the field 37 feet below grade.

Fresno State found itself in an even deeper hole Saturday afternoon not long after taking the field against a San Diego State team that controlled both sides of the line, was creative offensively and dominant — as usual — on defense.

SDSU once again thrived in all three phases, leading to the Aztecs’ to their fifth straight victory in a 23-0 Mountain West win over Fresno State before an announced crowd of 41,535. SDSU linebacker Tano Letuli capped the victory with a 31-yard interception return for a touchdown in the fourth quarter, then joined his defensive teammates to complete their third shutout of the season — a first in the program’s Division I history (dating to 1969).

SDSU (6-1, 3-0) became bowl eligible for the first time in three years while remaining undefeated in conference play. Fresno State (5-3, 2-2) remains a game away from qualifying for a bowl. The Old Oil Can trophy, which symbolizes this rivalry, rested on a table at the southwest corner of the field during the game. SDSU players were welcome to hoist it overhead after the win over the opponent they’ve come to call “The Team Up North.”

SDSU’s march to victory was briefly interrupted with more than a little concern when quarterback Jayden Denegal left the game after a 17-yard run early in the third quarter. Denegal suffered an apparent right arm/shoulder injury when he hit the ground and headed to the treatment tent. Backup Bert Emanuel Jr. replaced him, but Denegal (11-for-19, 124 yards, INT) returned for SDSU’s next possession seemingly no worse for wear.

The Aztecs and Boise State (6-2, 4-0 MW) are the only teams without a conference loss in MW play, with a showdown looming Nov. 15 at Snapdragon Stadium. SDSU hosts Wyoming and travels to Hawaii  before bringing in the Broncos.

Not that SDSU is looking ahead. The Aztecs remained in the moment against Fresno State, which made a surprise switch in quarterbacks.

Senior E.J. Warner, the nation’s active career yardage leader and son of Hall of Famer Kurt Warner, was benched in favor of sophomore Carson Conklin (17-for-38, 156 yards, 2 INT). Conklin threw for 3,600 yards in two seasons at Sacramento State, but this was his first start at the Division I level. He had thrown six passes this season.

If the Aztecs were surprised, it lasted for less than a full series. Fresno State had an 11-play drive on its first possession, moving 40 yards downfield, before the Aztecs stopped them and forced a punt. The Bulldogs’ next four possessions totaled 41 yards, ending punt, punt, interception, ball turned over on downs.

That last drive ended with six seconds remaining in the first half and SDSU leading 13-0.

It got worse from there. The Bulldogs got the ball to open the second half and were penalized on three straight plays. Just like that it was first-and-25 for Fresno State, which soon enough was calling on punter Nick Verdugo once again.

SDSU opened the scoring on running back Lucky Sutton’s 1-yard touchdown run, giving the Aztecs a 7-0 lead with 3:30 remaining in the first quarter.

The score was set up by a 53-yard pass play from SDSU quarterback Jayden Denegal to running back Byron Cardwell. Denegal faked handoffs to Cardwell and wide receiver Donovan Brown, then lofted a pass over the line to the running back 10 yards downfield.

Cardwell did the rest, his left knee touching down a yard before reaching the end zone (he celebrated anyway).

SDSU kicker Gabe Plascencia boosted the lead to 10-0 three minutes into the second quarter with a 42-yard field goal.

It was Plascencia’s 23rd straight field goal, an ongoing school record and new Mountain West record. Air Force’s Luke Strebel made 22 straight from 2015-16.

Plascencia made it 24 straight with 1:33 remaining on a 50-yarder that provided SDSU’s 13-0 halftime lead. The kicker initially made a 45-yard field goal, but there was a false start that moved the ball back five yards. Plascencia shrugged his shoulders and made it again.

The opportunity came after both sides traded interceptions.

Denegal was driving the Aztecs for a potential score when Fresno State cornerback Al’zillion Henderson outdueled SDSU wide receiver Will Cianfrini for the ball at the 3-yard line.

SDSU got the ball back moments later when edge Trey White burst up the middle to pressure Conklin, who threw a wobbler over the line that teammate August Salvati intercepted.

The Aztecs’ O-line opened big holes for the running game and provided the protection that allowed Denegal to cycle through all his receivers when he dropped back to pass.

Sutton (21 carries, 131 yards, TD) went over 100 yards for the third straight game on a 47-yard run that concluded the third quarter.

That set up SDSU with a first-and-goal from the 7-yard line as the final period began. The Aztecs lost two yards on the next three plays and Plascencia came on for a 27-yard field goal, his 25th straight, that made it 16-0 with 13:22 to play.