Oregon remained No. 2 behind Alabama, but Oregon State moved up to No. 10 in the latest AP poll.
USC is 11th and Stanford is 17th.
Last week, the Pac-12 had six ranked teams, but No. 23 Washington lost to the Ducks 52-21 and No. 25 UCLA was upset by California 43-17.
Arizona State, which plays host to Oregon on Oct. 18, and Washington both received votes, tying for 31st. Arizona also received votes.
South Carolina moved up to No. 3 behind the Ducks, ahead of No. 4 Florida. Those SEC East rivals play on Oct. 20th.
West Virginia is No. 5, Kansas State No. 6 and Notre Dame is No. 7. Kansas State visits West Virginia on Oct. 20, which looks like an excellent day for college football.
Stanford visits Notre Dame on Saturday. The Fighting Irish are at USC on Nov. 24.