Four of the Pac-12 Conference's five ranked teams got a tough test on Saturday and two were beaten.
Then there is Oregon, which has yet to let any team test it this season.
The second-ranked Ducks blew by Colorado 57-16 Saturday afternoon in Boulder to improve to 5-0 and keep alive their hopes of a national title.
Washington watched its conference title hopes take a hit with a 31-28 loss at Stanford, which remained undefeated. UCLA is also undefeated after surviving to beat Utah 34-27 on Thursday night while Arizona State went out of conference and lost to Notre Dame 37-34.
Stanford stayed a solid No. 5 in the polls behind the Ducks, who travel to face the Cardinal next month. UCLA moved up a spot to No. 11 while Washington dropped a spot to No. 16 and Arizona State fell out of the poll.
Washington State improved to 2-1 in conference play with its second Pac-12 road win of the season at Cal.
The nation will be watching the conference next week as ESPN GameDay will be in Seattle when the Huskies host the Ducks.
FIVE BIGGEST TAKEAWAYS FROM WEEK 6 IN THE PAC-12
1. Marcus Mariota may give Oregon its first Heisman Trophy winner. Mariota was considered one of the top three contenders for the award heading into the weekend and may have moved to the top of the list after throwing five touchdown passes while running for two more.
2. Some of the nation's top passing offenses are in the conference. Mariota threw for 355 yards against Colorado, but that was dwarfed by Connor Halliday's 521 for Washington State and Jared Goff's 489 for Cal.
3. Washington can play with the top teams in the conference, but must beat one this week to have any shot at the Pac-12 title. The Huskies fell to 1-1 with a loss at Stanford and return home to face Oregon. The North Division winner will likely not have more than one loss, so a defeat this weekend likely puts UW out of the race.
4. The balance of power in the Pac-12 is in the North, which has not lost a game to the South yet. North teams are a combined 10-4 in the conference while the South is 2-8.
5. Stanford is taking advantage of home-field advantage. The Cardinal have two conference wins over ranked teams, defeating Arizona State and Washington at home. Stanford also hosts ranked UCLA and Oregon this season.