The nail in Oregon's coffin came when their Heisman candidate quarterback had the ball stripped straight out of his hands while trying to drive for the game-winning touchdown at home.
With the clock ticking down to less than a minute behind him, Marcus Mariota stepped up in the pocket to make one more play, one more eye-popping escape. He shifted right but didn't feel the pressure. He didn't see Wildcats linebacker Scooby Wright though, who sacked him from behind and forced the fumble.
It was set to be a seminal moment in Marcus Mariota's career, a chance to prove that his video game numbers came with a real world clutch gene.
A loss like this wasn't insurmountable — playing in a tough Pac-12 conference will certainly help — but it doesn't help Oregon's case for being included in this year's inaugural college football playoffs.
Yet Oregon's problems went back before their loss to Arizona, which is now 5-0 and has pole position to win the Pac-12 South, along with Southern California.
No, Oregon (4-1) has struggled before today, showing that flashy dominance doesn't mean anything if it comes with shoddy malaise against tougher competition.
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Look for the early cracks in Oregon's dream season during its stunningly impressive 46-27 win over Michigan State.
Marcus Mariota faced a third-and-10 in the back end of the third quarter and was trailing the Spartans by nine points. He found himself in a pitch-option situation with freshman running back Royce Freeman, faced with a choice: to keep it or to pitch it.
That one decision was the margin of error for the Ducks.
He made the right choice, tossing the ball to Freeman despite his own reputation for athleticism, and watched as the freshman rolled for a first down. They would score the first of four unanswered touchdowns in that game.
But while that decision turned out well, it showed an uncomfortable truth: how close Oregon was to the edge of disaster this season. After all, if they hadn't scored then, the result could have been very different with the changing tides of college football momentum.
There were weaknesses again, which were exploited against Arizona.
If you squinted, you saw a little of last year's upset loss to the Wildcats in Thursday's game.
While the score wasn't nearly as lopsided — Arizona steamrolled Oregon 42-16 in 2013 — it revealed the Ducks' defense that comes and goes.
Last week, lowly Washington State put 31 points on Oregon. This week, it was more of the same, with Arizona's 31 points and 495 yards of total offense. Most devastating of all was the 208 yards rushing the Ducks allowed — yes, they kept Wildcat runners at a manageable 3.8 yards per carry average, but their inability to stop the run was exacerbated by poor tackling and bad positioning.
Things don't get easier for Oregon's defense. They tavel to face No. 8 UCLA's Brett Hundley-led attack next week, then have tilts against surprisingly competitive Washington and California teams before facing their arch-nemesis No. 14 Stanford.
There's no doubt that Marcus Mariota has the offense in order.
But if the Ducks defense doesn't step up, their season is already over.