BERKELEY — Cal defensive back Marcus Ezeff knows what it's like to play in a big game. He also knows what it's like to place too much importance on one.

So while Saturday's game against Oregon is the biggest of the season so far for the Bears, don't expect them to start believing that — at least not publicly.

"We understand that Oregon is in our way of the Pac-10 championship, and we're going to do our best to beat them," Ezeff said.

Ezeff had what was the defining moment of Cal's 2007 season — at least at the time — when he forced a fumble by Oregon wide receiver Cameron Colvin that rolled through the end zone for a touchback with time winding down. That helped preserve a 31-24 victory, one that moved the Bears to 5-0 and up to No. 3 in the national polls.

The Bears weren't shy about admitting it was a watershed victory. As it turned out, it was a landmark only because it marked the beginning of the end. Cal went on to win just one more regular season game and fell out of the national picture.

It's easy for an outsider to see why this is a big game. The Ducks are tied with USC atop the Pac-10 standings at 4-1; Cal and Oregon State are one-half game behind at 3-1. By the end of the weekend, there could be just two teams left with only one conference loss, helping the Pac-10 race take even more shape.

"You have to come into every week thinking it's a big game because the Pac-10 is so close," Cal nose tackle Derrick Hill said. "One mess-up can mean the difference between the Rose Bowl and a whole different bowl. The Pac-10 is so unpredictable. We see it week in and week out, so you have to go into every week thinking this is championship week."

To beat the Ducks, the Bears will have to find a way to slow down Oregon's high-powered spread option offense while getting their own offense in gear against the Ducks' playmaking defense.

The offense looks as though it will once again be led by sophomore Kevin Riley at quarterback. Coach Jeff Tedford said Tuesday that Riley is the starter, "as of right now." That's a deviation from the past three weeks, when Tedford said the position was completely open until the decision was made before the game.

Riley had modest numbers in Saturday's 41-20 win over UCLA, completing 11 of 22 passes for 153 yards and two touchdowns. But he wasn't intercepted and showed good mobility against the Bruins' pass rush, pressure the Bears can also expect to see against the Ducks.

"I thought Kevin played pretty well," Tedford said. "I think the difference in the game was decision-making. Kevin was harassed a little bit but held onto the ball and pulled it down when he needed to. He didn't make any poor decisions with the football, and that becomes critical in a close game. He made some pretty good throws, too. I thought Kevin played a good game last week."

Riley and senior Nate Longshore still split first-team reps Tuesday at practice. Although it seems Riley will get the nod Saturday, this still marks the fourth straight game the quarterback position has been up in the air when the week of practice began.

"The mind-set of being able to know who your guy is each week, there is a little bit of security when you have that," Tedford said. "But we're in a position where we need to make decisions each week until this thing separates itself. I've said all along that I don't like the two-quarterback system. I don't want to bounce back and forth if not need be. You'd like to have your quarterback settled on and take it from there."

Contact Jonathan Okanes at jokanes@bayareanewsgroup.com.