Just 11 days ago, Oregon was riding a seven-game winning streak and had broken into the top 10 in The Associated Press poll for the team's highest ranking since late 2007.
Since then, the high-flying Ducks have come back to earth.
Nineteenth-ranked Oregon (18-5, 7-3 Pac-12) was dealt its third straight loss on Thursday night. Colorado (15-7, 5-5) scored the final eight points of the game for a 48-47 upset, the Buffaloes' first victory in Eugene since 1955.
The loss snapped Oregon's 20-game winning streak at home, the third-longest in school history.
It also dropped the Ducks out of first place in the Pac-12 standings. Oregon now rests in a tangle for second with Arizona State (18-5, 7-3) and UCLA (17-6, 7-3) behind No. 7 Arizona (20-2, 8-2).