Oregon State's Cooper Hjerpe did what few pitchers have been able to do this year: shut down the Arizona offense.
Hjerpe (3-5) allowed just two hits and one run in seven innings, striking out 11 as the Beavers beat the visiting Wildcats 3-1 on Saturday night in Corvallis.
No. 9-ranked UA (37-14, 20-9 Pac-12) scored its only run in the sixth, when Kobe Kato stole home on a play where Donta' Williams was caught stealing at second base.
UA had only five total hits and walked just three times a night after notching 11 walks in a 12-4 victory in the series opener. Kato and Jacob Berry both doubled for the Wildcats' only extra-base hits as UA had its five-game winning streak snapped.
Garrett Irvin (5-2) took the loss, allowing three runs on nine hits in 6 1/3 innings. Oregon State (33-19, 15-11) scored a run in the first inning and two in the second.
The teams will play the rubber game of the series at noon Sunday on Pac-12 Arizona.
The Wildcats didn't lose any ground in the race for the Pac-12 title, as No. 13 Oregon (35-12, 18-8) lost at home to No. 17 Stanford 6-5. The Ducks' conference winning percentage of .692 is barely ahead of UA's .690.
Sunday will mark UA's last Pac-12 game of the year, while Oregon still has to visit Cal (28-23, 14-12) next week.
