And then there were five. Just two weeks ago, 10 undefeated teams still dotted the college football landscape, but in a show of pre-Halloween horror, that number was slashed in half by a run of road losses. In Week 8, Ohio State left Happy Valley distinctly unhappy, and in Week 9 Nebraska fell at Wisconsin, Baylor and West Virginia each stumbled in the Southwest, and Boise State’s promising season turned into a Men Without Hats music video.

Another factor all those upsets had in common: Each losing team had previously displayed a potentially fatal flaw that ultimately manifested as actually deadly. Nebraska, for instance, had struggled to open up holes for its running backs all season, leading to middling rushing numbers, and sure enough, the Cornhuskers managed only 3.5 yards per attempt and couldn’t move the ball against a swarming Wisconsin defense on Saturday. Boise State had narrowly escaped an upset against BYU in a five-turnover performance the previous week, but the Broncos again lost the turnover battle against Wyoming, with a fumble leading to a tie-breaking safety and Boise loss.

The good news for the remaining undefeated teams is that their flaws are less glaring. That makes sense: These teams are still undefeated because they’re really good and have fewer weak spots opponents can target. No team is perfect, though, and barring an unprecedented number of undefeated power-conference teams — never more than three since the beginning of the BCS — upsets are bound to strike.

So for four of the remaining unbeatens from Power Five leagues — as fun as a Western Michigan Playoff berth would be, P.J. Fleck’s bowmen limped behind three-loss Florida State in the first batch of selection committee rankings — let’s identify in advance what flaw might do these teams in and when it might reveal itself. And if these imperfections might seem small or insignificant, well, that’s what they said about a certain Greek warrior’s heel, and he suffered the ultimate defeat.

Washington: Pass Protection

Even with a pedestrian performance against Utah now blotching his résumé, Jake Browning still profiles as one of the country’s best quarterbacks. He’s second in passer rating and tied for third in both touchdowns and yards per attempt, and the sophomore QB would be the Heisman front-runner if Lamar Jackson hadn’t gone supernova this year.

But Browning can’t score when he’s on his back, and an opponent’s best chance at beating Washington might come from exploiting the Huskies’ offensive line. Overall, Browning has stayed relatively clean — a shade under two sacks per game — but that’s largely a function of the Huskies’ offensive efficiency and balance.

Washington has allowed sacks on a sixth of its dropbacks on “passing downs” — defined as second-and-8 or more to go, third-and-5 or more, and fourth-and-5 or more — which is tied for the second-highest rate in the country. In other words, when a defense has known a pass play is coming, it has brought pressure successfully.

Fortunately for Washington, its remaining schedule is light on pressure-heavy defenses: Washington State, Cal, and USC all rank in the bottom 30 in the country in total sacks. That leaves only Arizona State, whose defense is porous overall — giving up more than 36 points per game — but does this one specific thing well. Just in the last month, ASU amassed four sacks against Oregon, five against UCLA, and a whopping seven against Washington State. The Sun Devils are also on a three-game losing streak and might allow 50 points to Browning’s crew — but there’s the chance they make him miserable in the pocket and overmatch Washington’s line in obvious passing situations. That plan worked for Penn State against Ohio State, after all.

Clemson: Turnovers

Of the four teams on this list, none has come closer to losing than Clemson did against NC State. Only an acute case of College Kicker Syndrome — State’s Kyle Bambard missed three field goals, including a straight-on 33-yarder as time expired — kept Clemson’s perfect record intact. And despite Clemson’s remaining schedule looking eminently manageable, that game illustrated how the Tigers might misstep over the next month.

Clemson turned the ball over four times against NC State, with the Tigers losing three turnovers in Wolfpack territory and a Deshaun Watson interception going for a touchdown the other way. For the season, only seven schools have committed more turnovers than Clemson’s 18. A large part of the problem has been Watson himself: He’s throwing interceptions 39 percent more frequently, on a per-pass rate, than he did his first two years in college, and he’s tossed at least one in six of seven games against FBS opponents this season.

Neither South Carolina nor Wake Forest has the offensive talent to beat Clemson in a shootout, but they’re tied for 15th in the country in turnovers forced (17) and could conceivably use possession swings to keep the score close. Possible ACC championship game opponent Virginia Tech could pose even more of a challenge: The Hokies have collected two turnovers per game, and an ugly, low-scoring title contest would be a fitting way for them to celebrate their first post–Frank Beamer year.

Michigan: Kick Coverage

By nearly any measure, Michigan’s defense is the best in college football. The Wolverines rank first in scoring defense, first in total defense, and first in passing defense; they rank first in opponent third-down conversion rate and first in opponent red zone scoring rate. Adjusted by opponent and factors such as turnover luck and field position, Don Brown’s unit is responsible for allowing only 1.7 points per game. That’s not a typo.

That statistical soufflé is all by way of saying that if a team wants to beat Michigan, it might want to try scoring when the defense isn’t on the field. Opponents won’t return a turnover for points, either — Michigan has surrendered the ball just six times all year — so by process of elimination, all that’s left is special teams. The good news for would-be spoilers is that this is the one area where the Wolverines have shown a modicum of vulnerability.

An opponent would do well to hold Michigan to field goal tries in the red zone, thus placing pressure on an unreliable kicking game. It could also take advantage of a weaker coverage crew. In an admittedly small sample, Michigan is allowing opponents 8.75 yards per punt return, representing a rare statistic in which the Wolverines place on the bottom half of the national leaderboard. The same is true of kickoff coverage, with Michigan allowing a number of lengthy returns this season.

Thus, while Ohio State in Columbus clearly represents their toughest test over the next month, the Wolverines would be foolish to overlook Iowa on the road. The Hawkeyes have four punt returns of 20-plus yards this year, one off from the national lead, and Desmond King is one of the country’s most dynamic return men. He’s already shown off his evasiveness in scoring on a pair of interceptions in his Iowa career, and if he adds a kick return to that tally, the Hawkeyes might put up a fight against Michigan.

Alabama: Big Plays

A perfect defense would abide by two overarching principles: Prevent offenses from moving the chains, and prevent offenses from picking up large chunks of yards all at once. As a demonstration that, indeed, no team is perfect, the Crimson Tide ace the first test but relatively struggle at the second.

Alabama’s defense ranks second in efficiency — roughly, keeping offenses “off schedule” from picking up first downs — but only 115th in guarding against explosiveness, which measures how far a team moves the ball on plays when it’s efficient. To use a cross-sport analogy, you can think of efficiency like batting average and explosiveness like isolated power, which makes Alabama’s opponents the Adam Dunns of college football: They either whiff or they homer.

Or, if the numbers themselves are a bit confusing, just look at the company the Crimson Tide keep. In terms of defensive efficiency, Alabama is in the neighborhood of Michigan and Florida; in terms of explosiveness, it’s alongside such gridiron powerhouses as New Mexico and New Mexico State.

Even though Alabama has already weathered several explosive offenses to stay unbeaten, Nick Saban’s group still has two tests to come this month. LSU ranks second in the country in offensive explosiveness, and Auburn’s running game and offensive line have been dominant in recent weeks — which is especially problematic given that Alabama’s explosiveness problems have concentrated predominantly in its rush defense.

To cherry-pick just one illustrative stat, only nine teams are averaging at least one rush of 40-plus yards per game, and both LSU and Auburn are members of that selective group. (So is Alabama. The Tide are impossible.) LSU’s Leonard Fournette returned from injury with three lengthy touchdowns in Week 8, backup Derrius Guice is no slouch in the big-play department, and Auburn’s Kamryn Pettway has six touchdowns in his past three games.

They might spend their respective afternoons against Bama running into walls at the line of scrimmage, but few backs in the country are better suited to break a big gain or three. Though given how great Alabama’s offense has also been this year, they might need to verge on the “three” side if they want even a chance at an upset.