After three quarters, Washington State University was on the doorstep of its first Pacific-12 Conference victory under first-year coach Kirby Moore.

And what a win it would be - upsetting 21st-ranked Boise State.

Then, the have-nots, good-for-a-half Cougars, showed up in time to surrender three fourth-quarter touchdowns. The Broncos got out of Gesa Stadium with a 31-10 victory Saturday night - their first-ever win in Pullman.

Dylan Riley rushed for a game-high 128 yards - 110 coming in the fourth quarter when the Broncos needed their star running back to kick it into gear. He did, scoring on touchdown runs of 33 and 72 yards.

Boise State broke a 10-10 tie on Maddux Madsen’s 6-yard touchdown pass to Cam Bates with 13:33 remaining - 7 1/2 minutes after Jack Stevens tied it for the Cougars on a 47-yard field goal.

Here are three instant takeaways in WSU’s loss to the No. 21 Broncos in Pullman:

1. One costly turnover changes everything

For three quarters, the Cougars played their best complimentary football of the season.

On offense, they were sustaining drives, converting third downs and not turning the football over.

On defense, WSU was getting Madsen and company off the field.

Then came the deflating moment with the Cougars trailing 17-10 with 12 1/2 minutes to go - Owen Eshelman’s unforced interception off a miscommunication with running back Kirby Vorhees.

It appeared Eshelman was waiting for Vorhees to plant and cut before throwing a short timing pass in the middle of the field - except the tailback took an extra mini-step and cut the route outside.

Eshelman threw inside to nobody but Boise State linebacker Boen Phelps, who made one of the easiest interceptions you’ll ever have playing football at the Cougars’ 33-yard line.

Two plays later, Riley cut back to the right off a handoff and darted 33 yards for his first touchdown, and Boise State led 24-10 with 11:40 remaining.

2. Offensive line struggles continue to haunt WSU

It’s been obvious how much Moore has been in a slow burn over his offensive line’s performance over the past month.

When he’s been constantly asked about the offense’s struggles, especially recently after the appointment of Eshelman’s as the starting quarterback, Moore has repeated over and over that the protection needs to drastically improve.

It hasn’t. In fact, it has deteriorated.

At Utah State a few weeks ago, it was all penalties. Last week at Oregon State, Moore was miffed about how badly his blocking group was manhandled by a good Beavers’ defensive front.

Often on Saturday, Boise State sent its four defensive linemen and that was enough to create havoc and make Eshelman unsettled. The redshirt freshman was sacked four times.

Also, the WSU run game was held to its lowest output of the season - 53 yards on 33 attempts.

3. WSU still can't make the plays that win games.

Call it what you want - a slump, or a rut - but the Cougars cannot find that defining play to ride to a first victory over an FBS opponent.

On Saturday against one of the most efficient offenses in college football, the defense came dangerously close to picking off Madsen on two or three occasions - being in good position but failing to haul it in.

On Max Dean’s first punt of the game, Cam Bates flubbed the catch and the ball bounced on the turf.

Gage Jones, a linebacker on the punt-coverage team, saw the ball but slid right by it, unable to corral it for a turnover. The Broncos retained possession.

Might seem trivial, but these are the type of “winning” plays the Cougars are seeing, smelling, but not making in their hunt for that elusive and much-needed victory.

Boise State is. That is why the Broncos are 6-1 and tied atop the conference standings with Oregon State.