CORVALLIS —

Washington State was not supposed to spend Saturday celebrating a historic win on the field of Reser Stadium.

But there the Cougars were, deservedly savoring their first Pac-10 Conference football win since 2008 unabashed while the remaining few Beaver fans watched from the stands in stunned silence.

The Cougar players rushed to the WSU’s band and the visitors’ section of the stadium, filled with long-suffering Cougar fans, and sang the Washington State fight song jubilantly as Beaver players watched from the opposite end zone.

This was not supposed to happen. This was supposed to be a day when Oregon State notched an easy victory over the Pac-10’s most win-challenged team before running a three-game gauntlet to become bowl eligible.

But make no mistake, Washington State outplayed and outcoached Oregon State to the tune of 31-14 on a rainy and all-around gloomy day.

And after losing to UCLA last week, the Beavers are left with some soul-searching to do.

“I can’t remember the last time I wanted to cry after a football game,” said OSU tailback Jacquizz Rodgers. “It hasn’t been since high school. I love to win, and I wish everybody felt that way at times.”

How shocking was this game? WSU quarterback Jeff Tuel racked up more gross rushing yards than Rodgers, with 103 (79 net), as Tuel constantly evaded OSU defenders. Before Saturday, Tuel, who has been the Cougars’ starter since midway through the 2009 season, had never rushed for more than 34 yards in a game.

Now the Beavers are faced with this: having to beat USC next week and then beat at least one of the best teams in the country — either Oregon or Stanford — just to make a bowl game.

The Beavers have played in a bowl game in every season but one since 2001, missing out only in 2005. But after losing to one of the worst teams in the nation Saturday, that seems hard to imagine.

“We better do something really quick or we’re going to have an early break,” said Rodgers about his team’s need to win two of its next three games.

What went wrong against Washington State? It’s tough to tell other than to answer: “everything.”

The Cougars dominated Oregon State’s offensive front, for one. They sacked Oregon State quarterbacks five times and contained Rodgers to 93 yards on 15 carries.

And when something good did happen for the Beavers, something bad always seemed to follow — such as the trips Oregon State made into Washington State territory in the first half that ended in a missed field goal and a Ryan Katz interception.

But Washington State also came out with an attitude, evidenced by the late-hit penalty called against C.J. Mizell on Rodgers on the game’s first play from scrimmage. Not winning a league game in two seasons has a way of putting a team in a bad mood.

That play, despicable as it was, seemed to fire up the Cougars. And Oregon State could not answer the bell.

Though the Beavers looked flat until the second half, when they attempted to make a comeback with a pair of Katz-to-Markus Wheaton touchdowns that closed the lead to 24-14 in the fourth quarter, coach Mike Riley saw something else in his team.

“We just seemed tight and not cutting loose,” Riley said. “Afraid to lose is probably a very accurate assessment. Although, it sounds a little like a cop-out.”

The Cougars sometimes looked like the mistake-riddled team that has become the doormat of the Pac-10.

Washington State’s first scoring chance slipped away when Isiah Barton was flagged for unnecessary roughness, pushing the Cougars out of field-goal range on their first drive of the game.

And Washington State made a double dose of mind-numbing mistakes in the second quarter, when Cougar returner Aire Justin fumbled a punt and WSU was called for roughing the punter on the same play.

That play should have been exactly what the Beavers needed. Down 7-0, that fumble left the Beavers at WSU’s 24-yard line with a layup opportunity to tie the game.

But three plays and a missed field goal later, Oregon State was still without a score.

Not exactly the drive a team in a must-win game against the league’s worst team wants to see.

In all, the Cougars fumbled four times, losing two. And only one of those fumbles led to an Oregon State score.

Good teams take advantage of those kinds of mistakes. But Oregon State could not.

“We have not been playing good right now, and we haven’t really gotten better over these past few weeks,” said senior Beaver linebacker Keith Pankey. “And Washington State did, and that’s why they got the win.”

Now, a season that was once so promising is teetering on being lost thanks in part to a grinder of a schedule and two — to Washington and UCLA — that could easily have been Oregon State victories.

And now a loss in a game that most considered a gimme win for the Beavers — they were favored by more than three touchdowns — has them in a hole that is almost impossible to get out of with three games to go.

Can Oregon State win two of the next three?

“This team,” Pankey said, “can win three of the next three.”

But it is difficult to imagine a successful season that includes a loss to Washington State.

This OSU team did also beat a good Arizona team, and it went toe-to-toe with top-five teams TCU and Boise State on the road. But it will have to play its best football yet if it wants to go to another bowl game.

“We’ve played better teams and beaten better teams,” said Oregon State guard Burke Ellis. “So we know we can heal from this and make the 2010 Beavers a good story.”