The game was pretty much over Thursday night as soon as Patrick Christopher decided the Cal basketball team shouldn't play down to Oregon's level.

The senior guard scored 19 points in the final 6 minutes, 45 seconds of the first half and the Golden Bears moved back into a tie for first place in the Pac-10 Conference with an 89-57 win over the Ducks at Haas Pavilion.

Cal (12-6, 4-2) led just 17-13 entering the final seven minutes of the first half — and hadn't scored in nearly five minutes — when Christopher took over.

He scored his team's next 14 points — all in a span of 2:46 — extending the lead to 31-19.

But the Bears were just getting started. With a 15-0 finishing run, the Bears took a 48-21 lead into halftime, which prompted one compelling question: How in the world did Oregon (10-8, 2-4) beat the same Washington team that routed Cal 84-69 just last Saturday?

"Especially after a big loss, we needed this," senior Jamal Boykin said. "We were a team today."

The Bears and Ducks engaged in mutually sloppy play for stretches of the first half before Cal made 10 of its final 12 shots in the half to assemble a decisive 31-6 surge.

Christopher scored all 21 of his points in the first half.

"Pat was very good, and we did a good job of going to him," Cal coach Mike Montgomery said. "He was getting a little tired, but we said, 'Let's ride him.' "

Oregon center Michael Dunigan said the Ducks simply let Christopher take charge.

"If we don't follow the game plan, anybody could beat us," he said. "Coach said (Christopher) could do that if we didn't lock him down, and he did."

Cal senior Theo Robertson added 18 points, 12 of them in the first half, while point guard Jerome Randle, limping at times one week after injuring his right knee at Washington State, had 11 points and four assists.

Reserve guard D.J. Seeley matched his career high with 11 points, and Boykin scored 10 as Cal equaled its largest margin of victory over the Ducks.

Cal played its fifth straight game without sixth-man Jorge Gutierrez (sprained knee), but sophomore forward Omondi Amoke had 11 rebounds and provided a jolt of energy by diving for a loose ball early in the game.

"That's more like how we have to play. I thought Omondi Amoke was great," Montgomery said. "If we can sustain this type of energy, emotion, aggressiveness, we'll be fine."

Christopher said the Bears weren't discouraged by their loss at Washington.

"It's still early in the conference, and everybody's kind of beating up on each other," he said. "We aren't going to get down on ourselves for losing."

Oregon, which has held the lead for just 25 seconds in four consecutive defeats since beating UW 90-79 in Seattle on Jan. 2, continued its recent woeful shooting.

The Ducks entered the game shooting 35 percent over their three previous games and converted just 26.7 percent in the first half.

The Ducks finished the game at 38 percent from the field and were 1-for-18 from beyond the 3-point arc. Senior guard Tajuan Porter, the Pac-10's active career scoring leader, had just six points and is 12-for-47 from the field the past four games.