The evolution of the game to feature some of the better athletes at inside linebacker leads to a big problem for the game of football. The best kind of problem, the question of what to do with the explosive and violent players that used to be middle linebackers?
Surely there's room in football for athletes of this variety? Traditionally they've found their home running to the football from a stand-up position behind the defensive tackles. You can always move them to outside linebacker/rush-end, but that position is starting to get marginalized by the spread offense as well with only one player on the field at a time who can primarily be an "attack the line of scrimmage" type of athlete.
Then there's the 2-4-5 defense, which looks to get two traditional outside linebackers on the field as stand-up DEs, that can always make use of tweeners on the edge.
Another possible destination is nose tackle.
Traditionally, the nose tackle is a massive person with rare strength and power to demand and then ward off double teams and turn the middle of the field into a pileup while the linebackers run free to the football. If every team could find a >6'2", >320 pound human to dominate the middle of the trenches they would not hesitate to do so.
As rare as these players are at every level, they are especially rare for high school teams, who nonetheless still need players who can clog the middle of the field and command double teams so that the linebackers can get to the ball.
The solution at the lower level is usually to find quick, stout players that can either shoot the gap and make a tackle for loss or necessitate that the offense double team them and thus achieve the same aim as having a monstrous Hulk lined up in that spot.
The question is, why don't more college teams take a similar approach?
The challenges for the undersized nose tackle
One reason teams don't go small at nose tackle is that college coaches are under pressure to perform as a sort of minor leagues for the NFL. Although they'll make ultimately make some exceptions in order to win football games when the choice is clear, there is always some resistance to installing systems that don't translate to the next level and don't allow a team to recruit pro prospects.
This is particularly true on defense, where finding the best athletes is the most proven way to guarantee success.
There is no obvious pro parallel for a 6'2", 260 pound nose tackle who would have been an iso-stuffing mike linebacker in another era and if that player is a good athlete he probably doesn't want to play this position and erase his chances at being a draft pick.
Jay Ratfliff is the closest the NFL has come to this position type, a 6'4" 287 pound nose for the Dallas Cowboys who specialized in slanting into gaps rather than two-gapping, and his skill-type would generally find a home at end or 3-tech tackle in either college or pro ball.
The difficulty in projection can be seen at the high school level, where teams will occasionally use 200 pound athletes who project to other positions to stock their defensive line simply because there aren't other players on the roster who can perform that essential role.
The challenge in recruiting this position would be in finding marginalized tweeners or convincing obvious top players to play a thankless position that has little projection to the NFL. An undersized nose-guard has to be very quick and skilled or else he'll get run over and fail to achieve his objectives for the team, teams can't afford to play just anyone in this role.
The advantages for the undersized nose tackle
Despite the challenge of finding pro-level athletes who'd volunteer for this position, the pool of players to choose from here is still considerable.
There is the undersized but athletic defensive tackle, who will lose his athleticism if asked to bulk up to the preferred college weight of 280+, the explosive linebacker who struggles to keep his weight down in order to cover space, the shorter nose tackle who can stunt and shoot gaps but can't stand-up double teams with a bigger man's technique, the undersized pass-rusher who's one of the more talented players on the field but not talented enough to shine at the position every great athlete wants to play, etc.
In an age of up-tempo offenses, having a larger pool of talent to choose from is a massive advantage. The teams that have ideal, powerful nose-tackles often find that they are incapable of playing more than half the game, or too many consecutive snaps, without running out of gas and losing effectiveness.
Normally having a powerful nose tackle is an advantage for the bigger programs because they are so rare. The program that can regularly field 320 pound, two-gapping monsters is at a huge advantage over much of the rest of college football. However, if it takes two monsters to successfully combat up-tempo spread teams than the programs using monstrous nose tackles actually find themselves at a disadvantage as they are now relying on tactics they don't have the personnel to execute.
If the goal becomes to find players like Issac Gross of Ole Miss, a weakside defensive end recruit who has been a highly disruptive member of their defensive line for the last few seasons, then more teams will be able to boast effective DL play because the pool of talent for the position widens so considerably.
The next advantage to this technique is the rarity in which it's attempted.
Teams generally play smaller linemen at center who lack major size and power but are smart enough to organize the line and quick/skilled enough to be able to snap the ball and then move with enough speed to engage the DL. These types of centers often struggle when asked to snap the ball and then quickly engage with a 320 pound monster lined up across their face, but they may also struggle if defenses' took away their one key advantage: speed.
If the nose tackle is quick enough to get inside of the center and dart through an a-gap before the snapper is ready to handle him, there's not much recourse for the offensive line except to align the guards tight and double team him as quickly as possible so as to prevent all the negative plays the nose could then inflict.
If there's one place on the field the defense can afford to be very aggressive it's in the a-gaps, where penetration will take away angles for the running back and prevent him from turning downhill and interior pass-rush will ruin every kind of drop-back pass scheme.
When doubled, if that nose tackle is skilled enough to get low to submarine or split the double team, he can cancel out the gap and create a pile-up in the middle and free up the linebackers to run unencumbered to the football. You've now accomplished everything that a 320 pounder would have accomplished and you won't lose this player to the draft before his senior season.
Finally, the quicker nose tackle opens up a defense to a new world of possibilities. Since the chore of battling double teams and attempting to overpower OL is a serious one, traditional nose tackles are seldom useful for anything else.
The quicker nose tackle on the other hand can potentially threaten every gap between the tackles on a given snap. For instance on a standard fire zone blitz:
This style of blitz is effective enough with a traditional nose who's looking to fill space, occupy the center, and disguise the linebackers movements as they come flying in at angles to overwhelm one side of the protection.
If he's a more athletic player who can split a double team, beat a block with a pass-rush move, or make serious trouble in the event of an assignment bust between the center and guard then these types of blitzes become all the more effective.
Then there are long-sticking strategies that require speed from the nose tackle to even have a chance to work:
On a blitz such as this one the nose is trying to skip a gap and reach across two OL and to do it fast enough to take advantage of the guard if he's unable to turn his attention towards the nose in time. Very few two-gapping nose tackles will ever have much success on blitzes such as this one. If the nose isn't at least a mild pass-rushing threat then it's also harder to create confusion with stunts since the OL won't be distracted by the nose's movements out of fear that he'll blast through and get an easy sack.
Then there's dropping the nose into coverage, which has some famous successes with big men that are generally the exception that proves the rule, 300+ pound human beings aren't great in coverage. But if the nose is a 6'0", 255 pound athlete? It becomes more viable:
If a common strategy for the offense is to slip the running back into the middle against a blitz (especially if he doesn't realize the corner is coming off the edge), dropping the nose tackle into the shallow middle or having him pick up the running back can erase the QB's hot read and send him into panicked confusion, resulting in a sack or turnover.
Blitzes like this are common enough for some Under front coaches who like to use quicker nose tackles and could see a lot of value for modern anti-spread teams looking for answers on how to confuse and attack QBs and prevent them from getting too hot.
The easiest way to win a football game is to control the middle of the field, which is something modern defenses are often struggling to do in a meaningful way against spread-option teams. Part of the problem is that defenses have understandably found themselves on the defensive too often, rather than having ways to attack and dictate to the offense.
By putting more explosive athletes in the middle, the defense has a chance to thwart an offense's intent before it can get going. The move of more speed to the inside linebacker positions is a start, but it also frees up resources in the form of powerful athletes who can move quickly over short distances that might now be deployed as (mostly) full-time trench players.
As spread teams try to make the game more about speed, defense can always oblige them and see if they like the results when the tables are turned.