TUCSON, Ariz. -- The Arizona defender had fallen down, and USC receiver Robert Woods was all alone running down the sideline. Quarterback Matt Barkley leaned back and heaved the ball. Woods ran, the ball arced. It looked like a sure touchdown, one that probably would have started the conversation about the Trojans' huge game with Oregon the following weekend.

Woods ran. It felt perfectly scripted, a pair of superstars hooking up and making a definitive statement together.

Then the ball thudded to the turf a few yards in front of Woods. Barkley flat-out missed what should have been an easy 87-yard touchdown midway through the third quarter that would have pushed the USC lead to 22.

"I'll be thinking about that play all night," Barkley said. "I got a little too excited. I just didn't put enough air under the ball."

When your singular goal is a national title, every play matters. The details matter.

What happened next is Arizona took over the game, scoring 26 consecutive points, then holding on at the end for a 39-36 victory, with a Barkley Hail Mary pass falling harmlessly to the turf on the game's final play.

Just like that -- poof! -- USC's national title hopes died. The Trojans, who in the preseason looked like they were again ready for their national close-up after an NCAA-imposed two-year hiatus, now merely become the potential spoiler when the Ducks come to the Coliseum hoping to keep their national title run alive.

Arizona outlasted USC in this infinitely sloppy four-hour affair. The Trojans lost despite one of the all-time great performances from Marqise Lee, who broke the Pac-12 single-game receiving record with 345 yards on 16 receptions with two touchdowns. He also had a 72-yard kickoff return that set up a quick touchdown with 4:40 remaining that briefly perked up USC's hopes.

All USC needed to do was get a quick stop on defense. It didn't. The Wildcats got two first downs, forced USC to burn its final two timeouts and left Barkley and company with just 55 seconds from their 13-yard line to make a miracle comeback.

But this USC team, which seemed destined for greatness in the preseason, couldn't find that miracle.

And now the hard question: With its chief goals dashed, how will the Trojans (6-2, 4-2 Pac-12) react?

"We stick together," Barkley said. "That's the beauty of football. You experience the most exhilarating moments of your life and you learn how to cope and deal with some of these losses."

He then added, "We can still do something special."

USC could still go to the Rose Bowl. It could still win the South Division and then win the Pac-12 title game. Or it could collapse, losing four or five games. None of USC's final four games -- Oregon, Arizona State, at UCLA and Notre Dame -- are gimmes.

While Arizona (5-3, 2-3) played well in the second half, asserting itself as the Trojans seemed to wilt, the Trojans also were stunningly mistake-prone. Two of the Trojans' five turnovers were baffling Barkley interceptions. Arizona had only one turnover, a Jawanza Starling interception that he immediately fumbled back to the Wildcats on his return.

USC also surrendered a 60-yard pass from Arizona quarterback Matt Scott to Austin Hill on a third-and-22 play from the Wildcats' 16-yard line. That play set up the Wildcats' go-ahead score early in the fourth quarter.

"There are plays in every game that haunt you," USC coach Lane Kiffin said.

Kiffin further expressed bafflement at how penalty-prone the Trojans are. USC was flagged 13 times for 117 yards. Of course, Arizona had 14 penalties for 129 yards, So, yeah, it was sloppy for both sides.

Arizona coach Rich Rodriguez immediately noted that his team "didn't play very well." But he also liked what beating the Trojans means for his team.

"I think it makes us more relevant -- it should," he said. "I don't think we're a top-10 team, we've lost three games, but it gives us confidence. I hope it makes people notice. I hope it makes recruits notice."

On this day, Arizona's chief relevance came in making USC irrelevant nationally.

In one of the most celebrated moments of the offseason, Barkley stood in front of a Christmas tree last December in Heritage Hall and announced he was returning to USC for his senior season to take care of "unfinished business."

It will remain that way.