Dennis Dixon will have surgery on the left knee that buckled early in second-ranked Oregon’s upset loss to Arizona, spoiling his chance to win the Heisman Trophy.

The quarterback tore his anterior cruciate ligament during Oregon’s Nov. 3 victory over Arizona State, according to coach Mike Bellotti, but he had rested it and felt as if he was ready to play Thursday night against the Wildcats.

Now Dixon will miss the rest of this season.

“He’s a little bit despondent, because he obviously wanted to continue to play,” Bellotti said.

The versatile Dixon was one of the front-runners for the Heisman after he put the Ducks in line for the national title. Oregon had started the season unranked, and was picked to finish sixth in the Pacific-10 Conference.

Drawing comparisons to Vince Young, Dixon completed 67.7 percent of his passes for 2,136 yards, 20 touchdowns and four interceptions. The senior from San Leandro, Calif., also ran for 583 yards and nine scores.

Thursday night’s 34-24 loss to the unranked Wildcats knocked the Ducks (8-2, 5-2) out of the national title picture. Oregon was ranked behind LSU and ahead of Oklahoma and undefeated Kansas.

Dixon’s left knee crumbled as he tried to plant on an option carry with about 5 minutes to go in the first quarter against Arizona (5-6, 4-4).

His recovery after surgery will take some six months, said team physician Bob Crist. The date for the surgery wasn’t set.

Dixon was not available for comment.

Dixon first injured his knee in Oregon’s 35-23 victory at home over Arizona State on Nov. 3. While he knew the extent of the injury, he felt he could still play.

“He asked us on behalf of himself and his family to keep that quiet,” Bellotti said in a conference call with reporters Friday afternoon.

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It was Dixon’s intention to delay the surgery until after the season, the coach said. He continued with the understanding that any further instability in the knee meant he would have to stop playing, the coach said.

“While he certainly had some personal goals at stake, anyone who is familiar with Dennis knows that any decisions he made were purely in the interest of his teammates and not motivated by any personal gains,” Bellotti said.

He wore a brace Thursday night and said he had no pain or signs of trouble earlier in the game when he ran 38 yards for a touchdown on the Ducks’ first possession.

“It shows you’ve got to play your heart out, because you never know when you’re going to get that last play,” Dixon told a group of reporters after the game.

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Before he left the game against the Wildcats, Dixon completed five of eight passes for 62 yards.

Senior Brady Leaf, who replaced Dixon, completed 22 of 46 passes for 163 yards and threw two interceptions. Leaf, the brother of Ryan Leaf, was expected to start when the Ducks visit UCLA next weekend.

As for the Heisman, Dixon said after leaving the game Thursday night that he never really played with it in mind.

“I never did. My teammates know that. I’m playing for them and just having fun in the process in my senior season playing college football,” he said.

Dixon finishes his college career as the Ducks single-season leader in completion percentage at 67.7, surpassing Kellen Clemens’ 64 percent in 2005. He completed 63.9 percent of his passes, also leading the Ducks’ career list.

He ranks second on Oregon’s list for most yards rushing by a quarterback, trailing Reggie Ogburn, who had 644 yards in 1979.