Oregon's goal as the Ducks prepare to face UCLA is to put Arizona in the past. Quickly.

"You can't have your whole season decided by this one game, because then it's all downhill from there," freshman running back Royce Freeman said.

The Ducks (4-1, 1-1 Pac-12) were upset by Arizona 31-24 on Thursday night, a stunning defeat at home that on Sunday helped jumble the AP Top 25. The Ducks were among five teams in the top ten — along with Alabama, Oklahoma, Texas A&M and UCLA — that lost in a wild week.

Oregon fell to No. 12, while the Wildcats, off to a 5-0 start for the first time since 1998, popped into the rankings at No. 10 for the biggest leap since the poll went to a top 25 in 1989.

Coach Mark Helfrich gave his team Saturday and Sunday off before the preparation for the trip to UCLA begins in earnest. The now-No. 18 Bruins (4-1, 1-1) fell to Utah 30-28 at the Rose Bowl on Saturday night, and no doubt the Ducks were closely watching that game.

On Monday, they get back to addressing the questions raised in the loss.

Fans blamed some debatable calls, including a late unsportsmanlike conduct penalty against Tony Washington, who bowed to the Autzen Stadium crowd after sacking Arizona's freshman quarterback on third-and-8.

Because of the penalty, the officials moved the ball half the distance to the goal line with an automatic first down. Three plays later, the Wildcats scored the go-ahead touchdown.

The Ducks also have been besieged by injuries, including a possible injury to quarterback Marcus Mariota.

Mariota threw for 276 yards and two touchdowns, and also caught a TD pass from Freeman. He still has no interceptions this season, but he lost the ball to the Wildcats when he was sacked on what would be Oregon's final drive on Thursday night.

Mariota was sacked five times after seven in the Ducks' previous game at Washington State, a 38-31 Oregon win to open the conference slate.

Afterward, offensive coordinator Scott Frost suggested that Mariota wasn't "100 percent" after getting beat up against Cougars. As a policy, Oregon doesn't discuss injuries, so there's no way to know that extent of what was bothering the Heisman hopeful.

Mariota certainly wasn't the only Duck who has been impacted by injuries. Oregon's offensive line has been hit hard, with starters Tyler Johnstone, Andre Yruretagoyena and Jake Fisher all injured. True freshman Tyrell Crosby and walk-on Matt Pierson started their second game at tackle.

The Ducks lost defensive lineman Arik Armstead to a left ankle injury during the first half against Arizona. His status for UCLA is now known, but the 6-foot-8 Armstead's presence would be missed.

The loss also put attention on Oregon's running game, which managed 144 yards against the Wildcats. This season the Ducks, usually known for their stout ground game, are averaging 187.2 yards rushing per game. No running back has rushed for 100 yards or more this season.

Then there were mistakes: Oregon had 10 penalties for 79 yards. Center Hroniss Grasu was uncharacteristically called for a false start and two holding penalties. And there was crushing penalty that went to Washington.

"Execution, discipline, a bunch of things that we control were not good enough," coach Mark Helfrich told reporters Friday after digesting the loss. "It was not good enough to play the schedule we play. We need to play more cleanly in every phase."

The Ducks' straight path to college football's first playoff may have taken a hit, but after what happened over the weekend — both nationally and in the conference — they are not out of it by any means.

Cal is atop the Pac-12 North standings because the Golden Bears (4-1, 2-1) have played three league games, while Oregon Stanford and Oregon State are all 1-1 in league play. Arizona tops the South Division as the only undefeated team in the conference.

"Every loss is a test of our character to see how we respond," cornerback Ifo Ekpre-Olomu said. "Not every team in college football is going to go undefeated so everyone has to learn from their losses and get better."