EUGENE, Ore. (AP) — For the second time this season, Oregon State took a halftime lead against Oregon, and for the second time this season, the Beavers let a win against the Ducks slip away.

No. 24 Oregon overcame 31 points from Roberto Nelson to beat Oregon State 85-75 on Thursday and sweep the Civil War season series.

"When you're playing against a team that's ranked in the Top 25 and going for a Pac-12 championship, you can't play one-half of a game," Oregon State coach Craig Robinson said.

But for the second time this season, that is exactly what the Beavers did. Oregon State led 34-28 at halftime of the Jan. 6 game in Corvallis but lost 79-66.

This time, they led 41-34.

"Naw, I knew we were going to win," Oregon forward E.J. Singler said when asked if he was worried at halftime.

The Ducks did, and it wasn't even that close.

Carlos Emory scored a career-high 21 points for Oregon (23-6, 12-4 Pac-12), which took a one-half lead in the conference over idle UCLA.

Arsalan Kazemi had 17 points and 12 rebounds for the Ducks, Tony Woods added 16 points, and Johnathan Loyd scored 12.

"It was a good win for our team," Oregon coach Dana Altman said. "We really battled back in the second half. We're still in the conference race and I reminded them of that. We had a lot to play for."

The win was the fifth in six games for Oregon, which improved to 17-2 at Matthew Knight Arena this season to tie the school record for wins at home.

Oregon trailed 51-46 near the midpoint of the second half before going on an 18-3 run to take a 64-54 lead with 8:59 to play.

Woods scored seven points during that stretch, and point guard Dominic Artis, who missed the previous nine games with a foot injury, gave the Ducks the lead for good with a 3-pointer that made it 55-52 at the 11:29 mark.

Oregon maintained a double-digit lead for the rest of the game, peaking at 83-70 with 1:50 to play.

"I had full confidence in the guys. I knew we would regroup in the second half and we did," said Singler, who had nine points and six assists. "We came out and played really good on defense, got some turnovers and we executed offensively. I knew that we would come back and I wasn't really that worried."

Devon Collier added 14 points for the Beavers (13-16, 3-13).

Nelson, the Pac-12's leading scorer in conference games, was unstoppable in the first half, scoring 22 points on 9-of-13 shooting. He had nine points in the final 4 minutes of the half, including a 3-pointer at the buzzer, as the Beavers overcame a 29-25 deficit to lead at halftime.

Oregon State cooled off in the second half and went through a 5:30 stretch without a field goal and the Ducks took advantage with their game-changing run.

"We've got to start earlier," Singler said. "We've got to have better starts, especially these last two games away at Colorado and Utah. It's not something we want to do, coming back all the time."

Oregon appeared to suffer a devastating loss with 6:37 left in the first half when starting freshman guard and second-leading scorer Damyean Dotson fell hard to the court on a drive to the basket and had to be carried off the court and to the locker room by teammates.

Dotson, who had 21 points against Oregon State in the first meeting this season, returned to the bench for the second half but didn't play.

Altman said Dotson suffered a hip injury and could need a week to recover.

Emory took Dotson's spot in the lineup to start the second half and scored 15 points after the break. He finished the game 8 for 13 from the field.

The Ducks welcomed the return of Artis, who played for the first time since Jan. 23. The freshman played 12 minutes off the bench and finished with six points. His presence was especially critical in the second half when Loyd, who has started in place of Artis, picked up his fourth foul with 14:07 still to play.

"Man, what a difference he made," Altman said of Artis.

The Ducks shot 51 percent from the field — their best performance in 10 games — with 10 turnovers, five less than their season average. The Beavers shot 47 percent from the field and outrebounded the Ducks 32-28. But they also committed 18 turnovers that Oregon turned into 23 points.