PULLMAN - Within the first two batters Friday night, Washington State committed two errors. Those were followed by a pair of hits from top-ranked Arizona State, and the score was 2-0 almost instantly.

For a team trying to locate the rhythm it lost somewhere in Texas about a month ago, this was not the kind of start WSU had hoped to make.

But pitcher Chad Arnold and the Cougar batting order both responded beautifully, forcing the Sun Devils to join in a nip-and-tuck Pac-10 battle at Bailey-Brayton Field.

And in the ninth, the decisive blow was struck by the Cougars. Pinch-hitter Patrick Claussen skidded a first-pitch fastball up the middle, which drove in Matt Argyropoulos from third and gave WSU a 6-5 series-opening win over the team ranked No. 1 in all four major NCAA polls.

The Cougars (16-10, 2-2) clearly savored this one. After touching home, Argyropoulos led the rest of the Cougars on a sprint to first base, where they enveloped Claussen, a 182-pound sophomore.

"It was unreal: just a sea of red running toward me and getting tackled," Claussen said. "It was a great feeling."

Argyropoulos got the ninth-inning threat going by looping a double down the right-field line. He moved to third on Jay Ponciano's well-executed bunt, and then the left-handed Claussen was brought in after ASU called on Jordan Swagerty, a right-handed pitcher.

"That was actually perfect baseball the last inning," WSU coach Donnie Marbut said.

Claussen was looking for a fastball from Swagerty, a sophomore who tops out at 94 miles per hour. When Claussen saw a heater on the first pitch, he didn't hesitate to swing.

Claussen's opportunities have been limited this season by the emergence of freshman Brett Jacobs, but his attitude hasn't been affected, Marbut said.

"He's the best teammate on this team - and it's not close," the coach said. "He just will do anything for the team. He just wants the Cougs to win."

WSU's chances at winning looked sketchy when Zach MacPhee and Riccio Torrez drove in runs in the first inning. (Those hits came after throwing errors on shortstop Shea Vucinich and Arnold.)

But in the bottom of the first, the Cougars fired back with a four-run salvo. Michael Weber and Argyropoulos both cracked run-scoring hits.

And then Arnold, a right-handed junior from Kennewick, held the Sun Devils at bay, blanking them over the next three innings.

Some pitchers would "melt" after the sort of first inning Arnold experienced, Marbut said. "And the next thing you know, it would be 8-0.But Chad, he just buckled down and made pitches when we needed to."

The Sun Devils (27-2, 5-2) retook the lead in the fifth with three runs - two of which came on a homer from MacPhee. But Arnold and relievers Paris Shewey and Adam Conley kept them off the scoreboard the rest of the game. WSU tied the game in the seventh on an RBI triple from Garry Kuykendall that thudded off the wall in right.

Despite the raucous postgame celebration, the Cougars were focused on the rest of this series only moments later. They'll play ASU today at 2 p.m. and Sunday at noon.

"There's no question they're the best team in the country right now - heck, 27-1 coming in," Marbut said. "... They're a great club, they're well-coached and they've got good players, and if you can beat those guys, you feel like you can beat anybody in the country. But to do that, you've got to play consistent baseball."

NOTES - The Cougars now have a two-game winning streak over ASU and over teams that are ranked No. 1. The Sun Devils were also the nation's top-ranked club when WSU beat them in their final meeting last season at Tempe.

Arizona State 200 030 000-5 7 1

Washington State 400 000 101-6 10 2

Blair, Lambson (7), Swagerty (9) and Barnes. Arnold, Shewey (7), Conley (9) and Ponciano.

W - Conley (3-1). L - Lambson (3-1).

Arizona State hits - MacPee 2 (HR), Ri. Torrez, Ruettiger 2, Barnes (2B), Ra. Torrez (2B).

Washington State hits - Kuykendall 2 (2B, 3B), Jacobs, Jones, Weber (2B), Argyropoulos 2 (2B), Ponciano, Bartlett, Claussen.