Long story short, if USC loses any game, Cal beats Arizona, and WSU beats UW, WSU gets the #5 seed. That would be huge for any potential at large berth, and also make the road through the Pac-10 tourney that much easier. So the non-Coug teams to root for are Oregon and OSU (over USC) and Cal and Stanford (over Arizona).
Here’s why. Everything below assumes that everyone who plays Oregon from here out will win, UCLA will beat OSU, Arizona will beat Stanford, and WSU will beat UW.
WSU (8-9) plays only UW, on the final Saturday. If they win, they finish 9-9.
Arizona (8-8) plays at home versus Cal and Stanford. A likely split (they lost to Cal last time) and 9-9 record.
OSU (7-8) plays at Oregon, UCLA, and USC. They will likely beat Oregon, lose to UCLA, and beat USC. The USC is the game most in doubt. OSU beat USC at home in overtime. If they do so again, they'll have a 9-9 record.
USC (7-9) plays at home versus Oregon and OSU. They will likely beat Oregon and lose to OSU (see above). But if they pull the game out against OSU, they'll be 9-9.
If OSU beats USC and Cal beats Arizona, the relevant records for 5th place would be:
Arizona swept OSU but split with WSU. The language of the tie-break is a bit ambiguous, but based on my interpretation OSU would be out due to its losses to Arizona. WSU split with Arizona, so those two teams go onto the second tie-break. Both WSU and Arizona would split with UW (First place) and UCLA (likely second place) and both have been swept by Cal. But WSU swept ASU while Arizona was swept by ASU. The Cougars would then take the 5th seed.
If USC beats OSU and Cal beats Arizona, the relevant records will be:
USC swept WSU, and so WSU probably falls out of the running for the #5 seed. USC and Arizona split, but Arizona would get the tie-break based on its win over UW (USC was swept by UW). In that case, USC would get the #6, and WSU would get the #7 seed. That would mean they play Oregon in the first game, with a win over Oregon putting them against UCLA in Round 2, Cal (likely) in Round 3, and UW (likely) in the championship.
If Arizona beats Cal, WSU cannot get the #5 seed regardless of what happens between USC and OSU. In that scenario, if USC beats OSU, WSU would get the #7 seed. But if OSU beats USC, WSU would get the #6 seed. (WSU split with OSU, but would have a win over UW, which OSU does not have.) If WSU is the #6, they would play the #3 seed in their first game of the Pac-10 Tourney. Barring a gaffe by UCLA against Oregon or Oregon State, the #3 seed will be either ASU or California, which will probably be determined by the game between those teams at Cal, on the final Saturday. Cal won the first matchup by 10. After Cal, WSU would likely get the #2 seed (likely UCLA), and then the #1 seed in the (likely UW).
If (perish the thought) WSU loses to UW, they will be 8-10 and tied with the loser of the USC/OSU game for 7th place. WSU loses the tie-break with USC, and would therefore fall to the #8 seed, and an opening round matchup with Stanford. If they beat Stanford, they would get UW (#1 seed), then the winner of the #4-#5 game (ASU or Arizona, if Cal is the #3). Then they get to the title game, probably against UCLA. But if the tie is against OSU, not USC, then WSU wins the tie-break and gets the 7th seed.
So we need to root for any loss by USC and any loss by Arizona.