The Colorado Buffaloes made sure of that, knocking the Ducks from the ranks of the unbeaten 100-91.
Oregon reached their scoring average, but Colorado got theirs and some, setting a season-high with the 100 points.
Twice in the contest Oregon surged ahead to nine or more point leads, but each time the Buffaloes came back.
The Ducks opened the game on a 21-12 run. But Colorado scored 30-of-47 points take control.
Oregon used a 19-4 run to take their biggest lead of the game at 58-48, but it was another Colorado run that gave them an advantage the Ducks would not recover from.
The core of the issue was once again defense. Colorado's 56.4-percent shooting all but guaranteed an Oregon loss. And rebounding woes and untimely fouls proved fatal for the Buffs.
The Ducks were once again held below 50-percent from the field, finishing 33-for-78.
The Buffaloes have had the Ducks number since joining the Pac-12 in 2011-12. Oregon is just 1-5 against them and has lost four straight.