STANFORD, Calif. — The toughest test of the year for Stanford's defense just got a whole lot tougher.

STANFORD, Calif. — The toughest test of the year for Stanford's defense just got a whole lot tougher.

Fifth-year senior defensive end and co-captain Ben Gardner is out for the season with a left pectoral injury, handing the sixth-ranked Cardinal (7-1, 5-1, Pac-12) a major blow before facing No. 2 Oregon (8-0, 5-0) on Nov. 7. Stanford coach David Shaw said Gardner will undergo surgery to repair the damaged muscle.

Shaw said "there's a chance" that fellow starting defensive end Henry Anderson could return against the Ducks but he will make the final decision after Anderson practices this weekend, which both teams have off. Anderson has missed the last six games since he hurt his knee in a victory against Army on Sept. 14.

The timing of Gardner's injury could not be worse for Stanford's defense. Oregon is averaging 632.1 yards and 55.6 points per game. Both rank second in the nation behind Baylor.

"If we're not fully manned, it's ridiculously difficult," Shaw said.

Gardner hurt his left arm in Stanford's win over Washington on Oct. 5. He had played through pain — saying last week that, at times, his arm "shuts down" — until a collision in the third quarter of Stanford's 20-12 victory at Oregon State last Saturday sidelined him for good. Shaw said the injuries are unrelated.

Gardner, who made most of the defensive line adjustments, ends his collegiate career with 171/2; sacks and 34 tackles. He is hoping to land in the NFL, where he could be a possible late-round pick.