EUGENE, Ore. — The Oregon Ducks rarely, if ever, talk about injuries — even season-ending ones.

So it's hard to say how depleted the AP's No. 1 team is going into Saturday's game against No. 14 Stanford. But it's clear the Ducks have taken a hit, especially on defense.

The latest casualty is free safety Avery Patterson, who seriously injured his left knee in the second quarter of Oregon's 59-17 victory at California last Saturday night.

Patterson was seen on the sidelines on crutches and in sweats following the game. Although there was no official word from the program, The Oregonian newspaper cited an unnamed source as saying Patterson was out for the season.

Patterson had taken over as starter for senior John Boyett, who was hurt early this season. Boyett played in the opener against Arkansas State, but was in street clothes the next week. Later he revealed to his hometown newspaper that he needed surgery to repair the patellar tendons in both knees. While the Ducks never formally announced Boyett's injury, it ended his career at Oregon.

Sophomore James Scales replaced Patterson against Cal. Senior defensive linemen Dion Jordan (right shoulder) Isaac Remington (foot) and Ricky Heimuli (right knee) were dressed on the sidelines in Berkeley but did not play. As a result, the Ducks relied at times on three true freshmen — Arik Armstead, DeForest Buckner and Alex Balducci — on the defensive line.

Starting nose guard Wade Keliikipi never made the trip to Strawberry Canyon because of an undisclosed injury and was seen using crutches on Monday. Defensive end Taylor Hart also hurt an ankle or foot against Cal and wore a boot.

The injuries tested coach Chip Kelly's "next man in" philosophy.

"It's part of college football," Kelly said. "Can you handle it, or can you not handle it?"

The Ducks were already hurting in the secondary with sophomore backup cornerbacks Dior Mathis and Troy Hill absent against Cal for unclear reasons. The situation has become so serious that there was speculation this week that the Ducks might use wide receiver Keanon Lowe or even multi-purpose back De'Anthony Thomas on defense.

The move comes after USC used dynamic wide receiver Marqise Lee on defense for a few snaps against Arizona State last weekend, and Washington played receiver Austin Seferian-Jenkins on defense against Utah.

Lowe played at safety at Jesuit High School in Portland, and came to Oregon, in part, because he wanted to play offense. Thomas played on both sides of the ball at Crenshaw High School in Los Angeles.

"We're getting thinner, but we'll find a way to make it work," defensive coordinator Nick Aliotti said without naming names.

The Ducks already moved redshirt freshman Koa Ka'ai, who had played at tight end this season, back to defensive end, which he played in high school.

The bright side in all of this for the Ducks is that even though they've had injuries, their backups — and even third stringers — have had plenty of work this season. In addition to Oregon's practice of heavy player rotation on defense to wear down opponents, the Ducks often sat their starters after building up big leads against opponents this season.

"(That's) kind of the byproduct of winning some of those games early, getting a lot of those guys reps," Kelly said. "It wasn't like you turned around and said, 'Hey, you guys gotta play.' They'd been in games before and they had an understanding, and we had an opportunity to correct mistakes."

Against the Golden Bears, the injuries were not limited to the defense. There were two major scares on offense.

Senior running back Kenjon Barner left the game briefly during the first quarter after an apparent injury to his right thumb. Barner, the nation's fourth-leading rusher with an average of 136 yards a game, finished with 65 yards rushing at Cal.

And quarterback Marcus Mariota also left the game after a hard fall injured his left shoulder late in the first half, but returned and finished with 377 yards passing and six touchdowns.

Barner and Mariota say they're fine for Saturday's game against Stanford.

Cardinal coach David Shaw said Oregon is going to be tough no matter who they have on the field.

"Those guys are good football players. Everybody that they put in knows their scheme. They still play fast, they still play physical and they get after you.

"As a college football fan, I was saddened to see when the quarterback got hurt against Cal. I was hoping that he'd take about 10 days to nurse that injury," Shaw added with a laugh. "But he popped back in there and only threw four touchdown passes after he got hurt."