Notre Dame can thank its defense for being the primary reason the Irish are ranked No. 1 in the nation.
College football is full of high-flying offenses and video game numbers, but there's a constant that remains true despite what any other stat says: defense wins championships.
That's why six of the top ten defenses in the nation are on teams ranked in the Top 25, and why Notre Dame and Alabama are the top two teams in the country.
It's common sense—the team that scores more points wins, and if you can keep the other team from scoring, well, you have it in the bag. The SEC, a conference known more for defense than anything else, has become the most prestigious conference in the country by beating the opposition to a pulp.
Defense wins, and programs around the nation are learning that. If you're having any doubts, simply look at the stats in the game between Oregon and Stanford.
Teams have shown that a good defense can make up for a lot of deficiencies. The squads on this list have several issues, be it on offense, special teams, or a particular position on defense.
None of them are perfect (although Notre Dame, obviously, has the record to prove it). But their defenses are what sets them apart, and what makes them members of college football's elite.
Note: Teams are ranked by total yards allowed. Omitted from this list are BYU, Michigan State, Connecticut, and Bowling Green, who are all in the top 10 but are irrelevant in terms of big bowl games or conference championships.
Bjoern Werner has been one of the best players on the best defense in college football.
Florida State has had a bevy of disappointing seasons in the past few years, but none could be as disappointing as this one. The Seminoles are No. 10 in the BCS standings but could be in the national title picture if not for an inexplicable loss to N.C. State.
While the defense could be at fault for allowing the Wolfpack to score the game's final 17 points, it certainly can't be blamed for the overall performance it has given this season.
The year before Mike Stoops took over the defense, the Seminoles were allowing over 30 points and 400 yards per game. This year, the dominant front seven has allowed the 'Noles to give up a paltry 13.1 points per game.
Florida State has the best defense against the run, allowing just 70.6 yards per game. They also have the fifth-best pass defense. If you take away the mostly garbage time points that Clemson put on them early in the year, the defense only allows 10.7 points.
Put it all together and you have a unit that is simply the cream of the crop in the NCAA.
Alabama has only had one poor game defensively, and it nearly cost them a chance at a national title.
It's difficult to diagnose where Alabama's defense really is in relation to the other elite defenses around the country.
When the Crimson Tide play against weaker opponents, they are virtually impenetrable. When they play against stronger opponents, the defense still plays at a very high level—just not as elite as one might think.
In a near-loss to LSU, the previously invincible defense was shredded by the struggling Zach Mettenberger; in a crushing defeat against Texas A&M, Aggies star Johnny Manziel made mincemeat of the vaunted Crimson Tide front.
Still, Alabama only allows 10.1 points per game, tops in the nation, and the defense has carried the team for the entire year.
It may not be the best unit in the nation, but it's pretty darn close.
The Gators defense has held up its end of the bargain, performing well while the offense has struggled.
Florida doesn't do anything that makes you jump out of your seat with excitement (well, except for this), but they simply get it done with good, hard-nosed defense. Florida is only okay on offense, so the Gators have had to depend on their defense to get key stops at key moments.
Florida is superb against the run, and forces turnovers in the passing game. The Gators have 16 interceptions this year and have made life miserable for opposing quarterbacks.
In addition to posting two shutouts, Florida hasn't allowed more than 20 points in a game all season. Their lone loss came against Georgia, an ugly 17-9 affair where the defense played a phenomenal game.
Florida still has a very outside chance of playing in the national title game. If they find themselves there, the defense would be the primary reason.
LSU's defense has been an absolute terror for opposing teams this season.
Coming in at number four are the fighting Tigers of LSU. Since Les Miles took over as coach, the Tigers have been synonymous with defense, and this year is no different.
LSU only allows 281 yards per game and haven't missed a step despite losing Tyrann Mathieu, arguably their best player, to a season-ending suspension before the year began.
What separates LSU from the pack is the ability to force turnovers. The Tigers have forced 29 to lead the SEC, and it has led to many points for an offense that depends on the defense to stay in games.
Despite a few hiccups in recent weeks (like giving up 35 points to Ole Miss), LSU remains an elite defensive squad and will make a lot of noise during bowl season.
Manti Te'o has led the Irish, and has Notre Dame on the cusp of a national championship.
Every year, there seems to be one defensive player that separates himself from the others. First it was Ndamukong Suh. Then it was Tyrann Mathieu.
This year, it's former No. 2 overall recruit Manti Te'o, who has anchored a resurgent Notre Dame defense and has the Fighting Irish at a stunning No. 1 in the polls.
Notre Dame doesn't do anything flashy on defense. They don't force loads of turnovers and don't make bone-jarring hits.
What they do is they step up at critical moments and take away the oppositions best weapons. And don't forget, the Irish stepped up in a big win over Oklahoma early in the year—a place where the Sooners had lost only three times in the last 80 tries.
There's a reason Notre Dame is looking towards a national title, and that's because the defense has played at an elite level for the duration of one of the nation's toughest schedules.
If they end up making a championship appearance, it will be well-deserved.
Once again, Boise State has a dominant defense and once again, the Broncos look like the class of the Mountain West Conference.
Guess which team has one of the nation's best defenses again?
Of course, it's Boise State. The Broncos' are a perennial top-10 defense and are proving it again this year. They rank eighth overall in yards per game and only give up 14 points per outing. Chris Petersen's squad has been one of the premier defensive teams in the nation for several years now.
The defense's performance is the main reason why Boise State finds itself at No. 22 in the polls despite the departure of record-setting quarterback Kellen Moore after last season. The Broncos rarely give an inch, and are second in the nation with 32 turnovers forced.
Boise State may be out of the title picture for now, but if the defense can continue to play at a high level for a few seasons, the Broncos could get right back to busting the BCS.
It's been a strange season in Madison. Despite four losses, the Badgers still find themselves headed to the Big Ten championship game.
Why is Wisconsin relevant if the Badgers are 7-4?
Mostly, because Penn State and Ohio State are ineligible for conference championship appearances, meaning Wisconsin will play in the Big Ten title game by default.
But it's still surprising that the defense has had more of a hand in their success than the offense.
The Badgers were unstoppable last year but have looked pretty mediocre for most of 2012, and a lot of their wins can be attributed to a defense that has been absolutely suffocating. They've only allowed seven rushing touchdowns and haven't allowed more than 14 points per game since the end of September.
In a normal year, the Badgers wouldn't be playing for a Big Ten title. But due to the circumstances, the defense has carried them into a surprise appearance, and could push Wisconsin to a very unique Rose Bowl appearance.
Dreadful just a few short seasons ago, the Wolverines have really formed a solid defensive identity.
It was just a few years ago that Michigan simply couldn't stop anyone under Rich Rodriguez. Brady Hoke stepped in, and while the Wolverines took a step back on offense, the defense has really hit its stride.
Michigan's defense isn't exactly elite, but it gets the job done. The only issue is that it has struggled with more talented offensive teams like Alabama, Northwestern and Nebraska. This team could really become a force to be reckoned with, if it can clear up some issues and show up in big games.
For now, Michigan's defensive dominance lies in the stats. But somewhere down the road, it could be a defense that strikes fear in the heart of its opponents.
The boys in Ann Arbor have come a long way, and the future looks bright for the maize and blue.
The Gamecocks have made the traditionally offense-minded Steve Spurrier look like a defensive genius as coach.
Steve Spurrier has always been regarded as an offensive mastermind, but he has built a defense that is a true force at South Carolina. The Gamecocks rank 13th in the nation in defense and have played very well all year.
No description of USC's defense would be complete without mentioning Jadeveon Clowney, the sensational sophomore defensive lineman who has wreaked havoc on teams, since he first set foot in Columbia.
Clowney has 10 sacks this season and has had an immeasurable impact on the Gamecocks' front seven. He's an absolute beast who will be a top-10 draft pick in the future.
Even without talking about Clowney, this defense is very impressive. It may not be held to the same standard as the elite defenses in the SEC, but it's very close.
Rutgers dominated Cincinnati and proved that it could be a defensive powerhouse in the Big East.
Rutgers had a pretty solid 9-4 season in 2011, but the departure of Greg Schiano made people doubt whether or not the Scarlet Knights could keep it going.
Thanks to a dominant defense, Rutgers has jumped out to a 9-1, and is coming off of a superb defensive performance in a 10-3 win over Cincinnati.
Rutgers often gets left out of the conversation when discussing elite programs because they play in the Big East (soon to move to the Big Ten). But all things considered, this defense was stellar in 2012. It allowed 14 touchdowns all season and allowed 15 points or less in eight of 11 games.
A loss to Kent State is the only thing keeping the Scarlet Knights from entering this week's game against Pittsburgh undefeated. Still, it's been a superb season for Rutgers, and the future is bright for a team that has the defense to compete with anyone.