In its toughest test of the season to date, the No. 16 Stanford football team fell to No. 3 Oregon on Saturday night, 52-31, marking its first loss of the season.

The game was a tale of two halves for both teams. While the Cardinal (4-1, 1-1 Pac-10) held a 31-24 lead heading into halftime, it did not score in the second half while Oregon (5-0, 2-0) lit up the scoreboard with four more touchdowns.

“Things didn’t quite go our way in the second half,” said Stanford head coach Jim Harbaugh. “We didn’t handle some situations that could have put points on the board for us.”

Stanford came out strong and dominated the first quarter, forcing two Duck turnovers en route to taking a 21-3 lead. The Cardinal was quick to capitalize on its opportunities, scoring 14 points off a fumble recovery by Delano Howell and an interception by redshirt sophomore linebacker Chase Thomas.

Redshirt sophomore quarterback Andrew Luck was methodical in slicing up the Oregon defense, marching his team down the field for three touchdowns. He used numerous play-action passes with devastating effectiveness, notching numerous short- and medium-yardage gains on three-step drops to keep the offense moving. He capped the game’s first drive with a beautiful pass to junior receiver Griff Whalen for a touchdown and ran the ball in from 10 yards out on Stanford’s next drive for its second touchdown.

The quarter also featured a 44-yard touchdown run on the first play after the Chase Thomas interception from sophomore running back Stepfan Taylor, who has emerged as the featured back for the Cardinal offense.

In the second quarter, Oregon began to recover some of the momentum it had surrendered to the Cardinal. Duck quarterback Darron Thomas began to assert himself over the Stanford defense, hitting receiver Jeff Maehl with a 29-yard touchdown pass early in the quarter. Maehl completely fooled the Stanford defense, and Thomas hit him with no defenders within 10 yards.

After the touchdown, Oregon head coach Chip Kelly went for a dangerous gamble, electing to go for an onside kick. The Card was caught completely off-guard, and Oregon kicker Rob Beard recovered the kick with little difficulty to give the Ducks an opportunity to draw closer to Stanford. They capitalized on that opportunity in short order, going 54 yards down the field in less than two minutes to score on a LaMichael James touchdown run. Oregon moved the ball extremely well against the Stanford defense, with Thomas using a series of fakes and screens to pick up chunks of yardage on every play.

With the momentum firmly back on the Oregon sideline, the Cardinal returned to the field desperate to regain its composure and expand its suddenly slim four-point lead. Luck managed to drive Stanford down the field and hit redshirt junior Coby Fleener with a 36-yard touchdown pass, but the Ducks responded with a touchdown of their own on the next drive. Stanford entered the locker room with a 31-24 lead after notching a field goal as time expired in the half.

While Stanford was able to compete with Oregon in the first half, the second half was all Ducks. The Oregon defense shut out Luck and the rest of Stanford’s offense, while James and Thomas rolled up points against a suddenly weak Cardinal defense.

Over the final three quarters, the Ducks outscored the Cardinal 49-10, including a 28-0 run through the final two quarters. The Oregon offense finished with 626 total offensive yards, including 257 rushing yards and three touchdowns from James.

“I think it’s really hard to keep up with us because we practice so fast,” James said. “We put a lot into it in practice for the game. So when it comes to the third or fourth quarter, and we’re down by a touchdown or whatever, you know, we really feel confident because of our endurance and our tempo.”

Sophomore linebacker Shayne Skov, a defensive leader who had nine tackles in the game, did not mince words about Stanford’s second-half performance.

“Defensively, we just didn’t play a good game,” he said. “And they had a great offensive game…we made a lot of mistakes, and they played great offensively.”

The overall performance of the Stanford defense in the game renewed questions about whether the unit is strong enough to allow the Cardinal to be competitive in the Pac-10. Over Stanford’s first four games, the defense seemed vastly improved, shutting out UCLA and holding Notre Dame to 14 points—however, the Ducks’ offense was the first in a slew of strong Pac-10 offenses that new defensive coordinator Vic Fangio will have to scheme against, and it will be interesting to see whether the defense can respond with better performances against the remaining opponents on its schedule.

The Cardinal secondary, after showing flashes of brilliance through Stanford’s first four games, was highly ineffective. The defensive backs were methodically shredded by Darron Thomas, who finished with 20-29 passing for 238 yards and three touchdowns, in addition to running 15 times for 117 yards and another score.

Stanford’s physical front seven, led by Skov and senior linebacker Owen Marecic, was supposed to compensate for some of the deficiencies in the defensive backfield, but that unit was also gashed by the Ducks, who ran for 388 yards overall in the game.

On the offensive side of the ball, Stanford’s offense seemed to live up to the hype surrounding it throughout the first half, but faltered under the pressure and the hostile atmosphere in Autzen Stadium in the second half. Unless the offense can handle the pressure of playing from behind better, prospects for its remaining Pac-10 contests look somewhat dim.

A crucial play that came early in the fourth quarter illustrated some of the offense’s struggles. Down 45-31, the Cardinal faced a third-and-goal at the Oregon one-yard line, but Luck fumbled the snap and fell on the ball for a four-yard loss.

“That was my fault,” Luck said. “I pulled out too early and took the negative play.”

On the next play, Luck threw a pass intended for redshirt freshman tight end Zach Ertz in the end zone, but the pass was tipped and fell incomplete, turning the ball over to the Ducks.

Though Luck’s final stat line for the game was fairly strong—he went 29-46 for 341 yards and a touchdown—his two interceptions were very costly, and his final interception, late in the fourth quarter, sealed the victory for Oregon.

Stanford will try to regroup next weekend, as it finishes a slate of high-profile opponents with a home game against USC (4-1, 1-1). The Trojans lost at home to Washington on Saturday, 32-31.

The game will be nationally televised on ABC.