PHOENIX — The tremors started last season.

Southern Cal, the longtime undisputed king of the Pac-10, had its national title hopes dashed with an early loss to Washington, then fell three more times. Oregon, meanwhile, put together a team-on-the-rise season, losing just twice on the way to the Rose Bowl.

This season, USC, saddled with sanctions and little depth, was out of the Top 25 by the midpoint with a tough climb back after Reggie Bush’s Heisman Trophy giveback.

The fast-and-furious Ducks have raced up the polls, just below the top spot and in position for a national-championship run. And the rest of the conference, except perhaps one team, has become a tightly packed beat anyone, anytime bunch.

Once so stable for so long, the Pac-10 is the midst of what may be a massive power shift.

“The conference is definitely deeper now than it was,” USC coach Lane Kiffin said. “The other schools are doing a great job and it’s our job to make it like it was before.”

Before was USC on top, everyone else fighting for recognition away from the West Coast.

The Trojans were the Pac-10’s dominant team for the better part of a decade, a run filled with national championships, Heisman Trophy winners and conference titles.

Now, the Trojans are falling back to the pack as the Ducks appear to be separating themselves.

Oregon coach Chip Kelly has set the foundation of a program seemingly built for the long run, a 10-win season and a trip to the Rose Bowl followed by this year’s climb to No. 2 in the polls.

The Ducks have overflowing talent and speed on both sides of the ball, plenty of depth and a cat-and-canary ability to allow even good teams to think they have a chance just before delivering a crushing blow.

The recent run has turned Oregon, not USC, into the team with the national-title aspirations, the one everyone — even outside the conference — is talking about.

“We don’t run this football program based on outside influences,” Kelly said. “People saying you’re this or that, whether you’re good or bad. I don’t think you can do that. We don’t as a coaching staff talk about it. We as a group don’t talk about it. Our players, when I listen to them talk, they don’t talk about it either.”

The power shift isn’t just at the top. The other eight teams are jockeying for position, all but Washington State — despite its clear improvement — on relatively equal talent footing.