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The list of the unbeatens was shortened considerably this weekend. There were 27 undefeated teams prior to USC's ambush at Oregon State, and as of today, that list is now down to 18. In addition to USC, Wake Forest, Georgia, Nebraska, Minnesota, Florida, Colorado, Wisconsin and TCU all saw their records blemished in varying fashions.
Exactly half of the remaining 18 reside in the Big 12 (five) and SEC (four).
Here is a breakdown of each team's perfect start and their biggest hurdles remaining.
Best win: at Georgia, 41-30. Alabama rocketed up to No. 2 after a dominating performance against the preseason No. 1 team.
Biggest hurdles: Unbeaten Kentucky visits this week in a possible let-down game. A trip to LSU on Nov. 8 will probably decide the SEC West. Of course, there is the annual bloodbath with Auburn, and then a possible SEC championship game.
BALL STATE (5-0)
Best win: Navy, 35-23. The Cardinals also won at Indiana, but Navy gets the slight edge after wins over Rutgers and Wake Forest. Quarterback Nate Davis threw for four touchdowns in the win over Navy.
Biggest hurdles: A late November Wednesday night date at Central Michigan to face stud quarterback Dan LeFevour will be a challenge. Also, the MAC championship game will likely feature Bowling Green. A 10-0 start is not out of the question.
BOISE STATE (3-0)
Best win: at Oregon, 37-32. Boise built a 37-13 lead after three quarters and held on in the fourth.
Biggest hurdles: Another candidate for 10-0. Boise's final two games -- at Nevada and Fresno State at home -- will be big challenges.
Best win: UCLA, 59-0. BYU scored TDs on six of seven first-half possessions.
Biggest hurdles: Three big road challenges remain: TCU, Air Force and Utah, with the season-finale against the Utes shaping up as possibly the biggest game in Mountain West history.
Best win: at Louisville, 26-21. UConn erased a 21-10 deficit and won the game on a 45-yard interception return by Lawrence Wilson.
Biggest hurdles: A home game against West Virginia will be tough, but the Sunday night visit to South Florida on Nov. 23 is the toughest game remaining.
Best win: at Louisville, 27-2. Defense ruled the day in the opener, as UK scored two defensive touchdowns and returned an interception to the Louisville 7 for its other TD.
Biggest hurdles: All eight SEC games remain, which include road trips to Alabama and Florida and home games against Georgia and Vanderbilt.
Best win: at Auburn, 26-21. LSU rallied behind backup quarterback Jarrett Lee, who has taken over the job and made LSU a true national title threat.
Biggest hurdles: The Tigers go to Florida next, then play Georgia and Alabama at home before a possible SEC title game.
Best win: Illinois, 52-42. The defense was lacking, but Chase Daniel and Jeremy Maclin launched their Heisman campaigns with eye-popping performances.
Biggest hurdles: at Texas on October 18 (the week after Texas plays Oklahoma) will be tough, plus a likely date against Oklahoma or Texas in the Big 12 title game.
Best win: at Iowa, 22-17. The Wildcats held Iowa out of the end zone on four plays inside the 10 to record its second straight win in Iowa City.
Biggest hurdles: Northwestern misses Penn State and Wisconsin this year, so its toughest game remaining will be a home date with Ohio State in early November.
Best win: TCU, 35-10. The Sooners had trouble running the ball, but 411 yards through the air paced a big win over a good team.
Biggest hurdles: Texas, of course, but there are also visits from Kansas and Texas Tech and a trip to Oklahoma State before a possible clash with Missouri in the Big 12 title game.
OKLAHOMA STATE (4-0)
Best win: at Washington State, 39-13. Not much to pick from for the Cowboys, but a road win in the opener at a Pac-10 school is adequate.
Biggest hurdles: How about four teams currently in the top 7 (Missouri, Texas, Texas Tech and Oklahoma), with three on the road? Don't start dreaming about a perfect season in Stillwater.
PENN STATE (5-0)
Best win: Illinois, 38-24. Penn State passed its first test, although its 45-14 win over Oregon State also looks pretty good about now.
Biggest hurdles: If Penn State runs the table, the Lions will have to earn it with road games at Wisconsin and Ohio State.
SOUTH FLORIDA (5-0)
Best win: Kansas, 37-34. The Bulls won it on a last-second field goal after surviving an overtime game at Central Florida the week before.
Biggest hurdles: Another 10-0 start is possible here, with USF's final two games being against UConn and at West Virginia.
Best win: Arkansas, 52-10. Least lame of a very lame first four opponents.
Biggest hurdles: Oklahoma, followed by three more unbeaten teams (Missouri, Oklahoma St., Texas Tech) on consecutive weeks. Get through that, and there's still the Big 12 title game.
TEXAS TECH (4-0)
Best win: at Nevada, 35-19. A sloppy win against a middle-of-the-pack WAC team speaks to a very weak early schedule.
Biggest hurdles: All eight Big 12 games, four of which are ranked. Texas is at home while Oklahoma is on the road.
Best win: Ummm. at North Texas, 56-26? David Johnson threw six TDs. That's something, right?
Biggest hurdles: If Tulsa can get by Rice this weekend, its game at Houston stands as its biggest challenge before the C-USA championship game.
Best win: at Michigan, 25-23. Utah held off a late Michigan comeback at the Big House, something Wisconsin could not do this week.
Biggest hurdles: Its three toughest remaining games -- Oregon State, TCU and BYU -- are all at home.
Best win: at Ole Miss, 23-17. Vanderbilt forced six turnovers and rallied from a 10-point deficit to beat a team that went on to win at The Swamp a week later.
Biggest hurdles: Auburn and Florida come to Nashville, plus trips to Georgia, Kentucky and Wake Forest await. A bowl will still be a challenge for the Dores.