Last week provided the first major upset of the college football season, as Arkansas stunned previously unbeaten Auburn, part of a day that saw the number of undefeated teams culled to nine from 13. Stiff tests for at least four of those teams could cause that number to drop further this week.

NO. 24 RUTGERS (5-0) AT NAVY (5-1)
(Saturday, 1:30 p.m., CSTV)

Rutgers has built on last year’s success by learning how to win close games. The Knights have already survived difficult contests at North Carolina and South Florida, the latter in their most recent game two weeks ago.

Now Rutgers takes on Navy and its devastating option ground game in one of the final obstacles standing between the Knights and an undefeated record when they face Louisville November 9. Navy, like the other academies, uses the option — which relies on deception — to neutralize its lack of size on the offensive line. The Midshipmen lead the nation in rushing at 350.5 yards a game and have a habit of making even good defenses look bad. Led by quarterback Brian Hampton, Navy will produce some big plays in the run game, but Rutgers’s 11th-rated rush defense should be able to keep the Middies under their season average.

The Knights, who have one of the nation’s best running back tandems in tailback Ray Rice and fullback Brian Leonard, should be able to run against Navy’s undersized front. That’s critical for Rutgers’s success, as quarterback Mike Teel has struggled throwing the ball.The fact that Rutgers is undefeated and ranked despite such a limited passing attack is a tribute to Rice, Leonard, and the defense. If those units play as they have this season, Rutgers should move to 6–0 to become bowl-eligible for the second straight season.

NO. 1 OHIO STATE (6-0, 2–0 BIG TEN) AT MICHIGAN STATE (3-3, 0–2)
(Saturday, 3:30 p.m., ABC)

While pollsters debate who’s no. 2, Ohio State has been firmly entrenched in the top spot since its dominating win at Texas. Despite Michigan State’s awful play in recent weeks, this is the most dangerous game for Ohio State before facing Michigan on November 18.

Ohio State isn’t outstanding in any one area.The Buckeyes’ offensive and defensive national rankings are only pedestrian, but they have taken advantage of every mistake by an opponent to roll to 6-0. Only Penn State, which was within eight points in the final minutes, has challenged Ohio State this year.

Just as Ohio State has locked down the no.1 spot in the polls, Michigan State has latched onto another title: the nation’s most mercurial team. Again this season, the Spartans have proven to have the ability to both play with, and occasionally beat, the nation’s best teams and to lose to some of the worst. If Michigan State quarterback Drew Stanton can regain the form that made him a potential top draft choice, and if the Spartans can avoid mental errors, they have the talent to play with Ohio State. Will they? History suggests otherwise. This might be a game for a half, but look for the Buckeyes to pounce on the first Spartans mistake and cruise to a win.

NO. 2 FLORIDA (6-0, 4–0 SEC) AT NO. 11 AUBURN (5-1, 3–1)
(Saturday, 7:45 p.m., ESPN)

Florida can nearly see the light at the end of the tunnel. The Gators have already beaten Tennessee, Alabama, and LSU this season, and now face a road test at Auburn. Georgia and the SEC title game await, but a win over the Tigers Saturday would give Florida the strongest résumé for the second spot in the polls of any of the contenders.

For the first five games, Florida coach Urban Meyer used freshman quarterback Tim Tebow on the goal line and in short yardage, and he proved nearly unstoppable running the ball despite the complete lack of surprise when he did so. Against LSU last Saturday, Tebow ran for a short touchdown, but also twice pulled up to throw touchdown passes.

Chris Leak is still the Gators starter, and he has handled the job-share with aplomb. The senior is enjoying his best season, and with the Gators undefeated and in position to make a run at a national title, it’s doubtful he minds sharing the spotlight with Tebow.

Auburn coach Tommy Tuberville complained before last week’s game with Arkansas that the SEC was too tough to allow one of its teams to reach the national-title game. Perhaps he was right. Arkansas ran all over the Tigers on the way to a 27–10 win that gave the Razorbacks a de facto two-game lead in the SEC West and all but eliminated Auburn from the national-title chase.

The Tigers can likewise take a wrecking ball to Florida’s hopes if their stars get going. Quarterback Brandon Cox and tailback Kenny Irons produced precious little offense against Arkansas. They must do better against Florida’s opportunistic defense. Florida is not a power-rushing team that is likely to dominate the line of scrimmage the way the Razorbacks did, meaning that like many key SEC tilts, this one could be dominated by the defenses.

NO. 4 MICHIGAN (6-0, 3–0 BIG TEN) AT PENN STATE (4–2, 2–1)
(Saturday, 8 p.m., ABC)

Penn State has only one outright and one shared Big Ten title since joining the conference in 1993.A big reason for the limited success is the Nittany Lions’ struggles against Michigan. Even when it shared the conference crown last season, Penn State couldn’t get past the Wolverines, falling 27–25 on the final play of the game for its only defeat of the year.

That victory ran Michigan’s winning streak against Penn State to seven games, and the Wolverines are favored to make it eight at Happy Valley Saturday night.They’ll have to do so without the man who caught the winning pass in last year’s game, Mario Manningham, who will miss the contest following knee surgery earlier this week. Manningham has been one of the nation’s most dangerous deep threats, with nine touchdowns and a per-catch average better than 20 yards, so his loss should limit Michigan’s explosiveness.

Still, Michigan is deep at receiver, as Adrian Arrington has shown in recent weeks taking advantage of some of the double-teams shown to Manningham. Michigan also has a healthy Mike Hart at tailback, and he and quarterback Chad Henne, not Manningham, are the Wolverines’ most indispensable players.

If Michigan can get past this game and Iowa next week, it should reach the Ohio State game 11-0 and play for a berth in the national-title game.To do so, the Wolverines’ nationalbest rush defense must contain Penn State tailback Tony Hunt and pressure quarterback Anthony Morelli into mistakes. Morelli is talented, but erratic, and will turn the ball over if forced to leave the pocket.

Mr. Levine is a writer for FootballOutsiders.com