Since the start of the 2005 season, a No. 1-ranked team -- we're counting AP polls or BCS standings, depending on what part of the season it was -- has lost 15 times. It happened just once each in 2005, 2006 and 2008, but it has happened in each of the last three weeks. Because those three drops -- the Alabama Crimson Tide, Ohio State Buckeyes and Oklahoma Sooners -- all happened as they were the road team at the "College Gameday" site, many are focused on the Oregon Ducks heading to face the USC Trojans in Los Angeles.
In reality, though, the Mississippi Rebels -- the same team that opened the season by allowing 49 points to Jacksonville State -- could stun the BCS No. 1 Auburn Tigers on Saturday. There are four trends to knocking off a No. 1, however improbable it may seem. Ole Miss does have a shot here.
1. The battle on passing downs:
Teams pulling the big upset stay aggressive on passing downs and find some holes to poke in the No. 1 team's defense. The average passing downs S&P -- one of Football Outsiders' primary NCAA stats -- for winning teams in these games is 0.769, well above the national average. The losing (No. 1) team has an average S&P of 0.568; that means less than 30 percent of its plays in passing downs are successful.
When the Illinois Fighting Illini knocked off No. 1 Ohio State in 2007, their ground game got much of the press, and justifiably so. But their ability to move the chains in passing situations was both surprising and vital. Against one of the best defenses in the country, the Illini converted on 43 percent of their third downs (42 percent on the ground, 44 percent through the air).
Ole Miss has the seventh-ranked pass offense by Football Outsiders' evaluation; granted, Auburn is first. The key here will also be stopping the pass: the Rebels are 61st in that regard, and the Tigers are 26th.
2. Mix it up on first down:
When the South Carolina Gamecocks knocked off Alabama, they did so by passing effectively enough on first down to keep the Crimson Tide on their heels. They threw 33 percent of the time on first down, but they were quite successful in doing so.
On a per-play basis, Ole Miss has been surprisingly effective throwing the ball (14th in Passing S&P+). Jeremiah Masoli has made up for a lackluster completion percentage by completing long passes to the likes of Markeith Summers and Melvin Harris. However, the Rebels are consistently digging themselves holes on first down; they rank 96th in First Down S&P+ for the season. They are extremely predictable on these downs (they run the ball 70 percent of the time on standard downs, 17th-most in the country), and if they allow Auburn to attack the line of scrimmage without repercussions on first-and-10, they will likely find themselves in too big a hole to pull off the upset. The Auburn defense ranks 53rd against the pass on first downs; it is vulnerable if Ole Miss can take advantage.
3. Hold something in reserve:
Up five early in the fourth quarter last week, the Missouri Tigers unleased a hook-and-lateral against Oklahoma that likely gave Sooners fans major 2007 Fiesta Bowl flashbacks. You don't necessarily have to break out oodles of trick plays, but you have to execute very well.
Auburn has been in a lot of tight games this year -- in six of its eight games, it's been very close into the fourth quarter -- so there's a chance this one will still be a game late.
This challenge, too, falls as much to the Ole Miss defense as to the offense. The Rebels rank 72nd in Fourth-Quarter Defensive S&P+ and, more alarmingly, 112th against the run. Against quarterback Cameron Newton and an Auburn offense that has worn out defenses on the ground late in the game (the Tigers rank 14th in Fourth-Quarter Offensive S&P+, sixth on the ground), this is terrifying. Ole Miss fell apart late in that humiliating season opener against Jacksonville State; consider this an opportunity for defensive redemption.
At some point, fatigue might play a part in Auburn's season trajectory. Ole Miss has not shown the ability to take advantage of this -- along with their iffy defensive rankings, the Tigers rank just 72nd in Fourth-Quarter Offensive S&P+, 109th on the ground -- but they must find a way if the college football season is going to see a historic fourth straight No. 1 team fall.
4. Return the opening kickoff for a touchdown:
Well, maybe this isn't really a trend. But after watching it work the last two weeks for the Wisconsin Badgers and Missouri, why not a third straight week?
Bill Connelly is a writer for Football Outsiders who contributes frequently -- typically on Thursdays -- to ESPN Insider.