George Horton has kept Ryne Nelson in the bullpen this season for one of two scenarios.

The first option is for the right-handed pitcher to throw in multiple games during a weekend series, but that didn’t happen against Oregon State because the Ducks never got a lead on Friday or Saturday. So Nelson was fresh when Horton brought him into Sunday’s game with two outs in the third inning.

“We thought that was the spot to get him in there,” Horton said.

Nelson never left as he threw 120 pitches in 6 1/3 innings to finish off Oregon’s 3-2 win over No. 12-ranked Oregon State in front of 3,531 during a dramatic and emotional afternoon at PK Park.

“You got your money’s worth today,” Horton said.

Nelson was at his best when he struck out the side in the fifth inning after Oregon State’s coaches asked the umpires to check the dark spot on the right side of his hat.

“That’s where I rub my spit, but they must have thought it was something else,” Nelson said. “That got me pumped up for sure.”

Nelson’s next pitch struck out leadoff hitter Beau Philip and he followed up with a three-pitch strikeout of Joe Casey. Nelson capped the inning by striking out OSU catcher Adley Rutschman before pounding his chest and staring at the OSU dugout as he walked off the mound.

“They accused him of having an illegal substance and he wasn’t cheating,” Horton said. “They thought they saw something and it wasn’t true. That escalated his emotions right there.”

The drama reached a peak in the top of the eighth inning after Alex McGarry led off with a homer to get OSU within 3-2.

George Mendazona followed with a single and was sacrificed to second. With two outs, Philip was intentionally walked before Nelson walked pinch-hitter Zack Zalesky to load the bases.

Rutschman, a top contender for national player of the year who may be the No. 1 pick in the Major League Baseball draft, stepped to the plate and Nelson struck him out on a 1-2 pitch.

“That was really cool, their guy versus our guy, big on big,” Oregon third baseman Spencer Steer said. “That was going to decide the ballgame. I had 100 percent confidence Nelly would get him out.”

Oregon had nobody up in the bullpen entering the ninth inning when Nelson retired the first two batters before McGarry and pinch-hitter Andy Armstrong hit back-to-back singles. With runners on second and third, Nelson struck out Jake Dukart to end the game.

“Nelly did not have much left in the tank so I think he reached back on that last curveball and got it done,” Horton said.

Nelson, who began the season in the starting rotation and ranked among the top college pitching prospects for the MLB draft, suffered a walk-off loss in each of his previous three appearances. He allowed eight hits and two earned runs while striking out 12 against the Beavers to lower his ERA to 3.98.

“This is definitely big for my confidence after three rough outings did not go my way,” he said. “I knew I had to get back out there and give it everything I had.”

Oregon (25-24, 9-15 Pac-12) snapped an eight-game losing streak to Oregon State in conference play to avoid being swept by the rival for the third season in a row. The Beavers (33-15-1) fell into a three-way tie for first place in the conference at 19-5 with Stanford and UCLA.

Oregon took its first lead of the series with two runs in the first inning off OSU starter Christian Chamberlain. Tanner Smith walked and scored on a double by Steer. Jonny DeLuca followed with a single that scored Steer.

Oregon added a run in the second after Smith hit a two-out single and Steer walked. DeLuca singled in Smith before Steer was picked off at third base following a rundown.

UO starter Brett Walker tossed two scoreless innings and got an out in the third before Casey and Rutschman hit back-to-back singles. Kolby Somers came out of the bullpen to get Tyler Malone to fly out before Nelson got Ryan Ober to fly out and end the inning.

“They did it as we mapped it out,” Horton said. “That was good teamwork on the mound. We haven’t had a whole lot of that passing the baton from one pitcher to the other.”

Oregon State scored in the sixth when Tyler Malone walked and McGarry hit a one-out single. With two outs, Dukart singled in Malone to get the Beavers within 3-1.