NCAA college football programs are only allowed to have 85 players on scholarship.
It's a simple rule that's been taken for granted for a long time, but it has a profound impact on how teams are built. Consider the following:
Ideally a team would always have talented upperclassmen to stock all of their positions on the field and certainly they'd prefer that their QB was a talented junior or senior with a few years in the system.
Well how many quarterbacks does a team have to sign every year in order to guarantee that they have a talented upperclassman who can run the offense every year? Oklahoma and Texas have generally averaged about 1 QB per signing class. This means that they need to be 50% on their evaluation and development at QB to ensure that they always have two good players at the position.
To ensure that there's enough separation (what if the two good players are only a year apart?) to avoid a down year you'd need to hit even higher than 50% or you'd need to sign more quarterbacks.
This is the trickiest position to manage, and one that most often leads to boom or bust cycles for programs (Vince/Colt=Boom! Gilbert-concussed Ash/Case=Bust!). Coaches that can't avoid boom or bust cycles that seriously alter the fortunes of their teams get fired.
But how do you avoid it? You take more QBs? That might work, but if you are taking the cream of the crop every year you are likely to end up with players who will transfer if they don't get their chance to start sooner than later.
Do you take less talented or less polished players who will be more likely to stick around? Do you de-emphasize the role of the QB position in your offense?
Then there's the other positions on the field. Can you afford to assign more scholarships to QB or other essential positions without subjecting yourself to major boom/bust cycles at other positions? In today's economy when nations attempt to fuel growth with debt only to see speculation blow up in their faces, it's a relevant question to ask of university football.
"Hey new coach of University X making three million per year, what's your strategy for avoiding unwieldy speculation in high school talent futures?"
There are a few strategies teams can employ to avoid this problem and though they're rarely examined they are crucial strategies for strong programs. Anywhere you see a program with longevity of success, you will generally find a few of these strategies being utilized.
1) Recruit to a system and embrace the lower-ranked players
Scholarship limits DEMAND careful evaluation of players. If you bring aboard players who are a bad schematic or cultural fit, you increase your vulnerability if the other players you signed simply aren't very good players or have limited ceilings.
But, what if you have a strict structure to your team and have clear roles for the positions in your offense and defense? Everyone has to adapt to the talent they have, but that doesn't mean they don't have a system in mind with multiple possibilities when they choose their players.
If you know what your linebackers should look like, you can carefully recruit and sign the players that meet this description and ensure a higher hit rate of finding players that will make your system successful. Perhaps you even have certain positions where you take archetypes and others where you aim for talent and plan on being flexible and inventive.
For instance: A spread team may vacillate between utilizing a tight end or a versatile fullback with play books and schemes in place in the event that the team has a good tight end or has a good fullback worth featuring in the offense. See the Oklahoma Sooners in the Bob Stoops era.
Recruiting to a system is particularly effective for recruiting the more difficult positions such as QB or OL. If your quarterback has a list of needed competencies that is less than the sum total of all quarterbacking skills and attributes, you can take multiple three-star kids and find great success.
2) Invest more scholarships in key spots
Offensive and defensive linemen are notorious for not panning out consistently in the college game. If you are 6'5" and 280 pounds it might be great fun to destroy your peers at the high school level but when you get to college and are expected to eat, sleep, and breathe football in between grappling with other similarly massive people you may lose your drive.
Especially when surrounded by all the narcissistic temptations of being a young man in college, much less a semi-famous one. Linemen often get to college and eat their way out of top form, are unable to eat their way into top form, injure themselves, or flame out for any other dozen reasons that players aren't successful. They do so more often than other positions, however, because more can go wrong.
Given the importance in football of controlling the trenches, many teams rely on having advantages along the lines. To do that, you may have to invest more scholarships there.
Mike Gundy of Oklahoma St has determined that his team is good enough at developing offensive players and reliant enough on good DL play that he'd better utilize more scholarships on defense in order to keep his team stocked with impactful linemen.
Additionally, Oklahoma St can't necessarily attract all the top DL recruits so they need numbers in order to find project players with upside in the hopes that enough of them will develop to give them good defensive lines from year to year.
To do this, you'd better be really good at evaluating and developing talent at other spots. Another coach might say "we're great at developing linemen, but our wide receiver recruiting is a veritable crap shoot..." and weight his scholarships to ensuring the presence of weapons in his WR corp. It's all about leveraging your own advantages and resources.
This is the controversial strategy of Nick Saban and some other SEC programs and it works as follows: You sign enormous classes of players every year and you effectively cut older players that haven't panned out in your program by forcing them to transfer to another school, having them retire if they have finished their degree, or "encouraging" them to take a medical hardship to clear the scholarship spot for a new, young player.
When considering the practices of some major institutions, the insistence by the NCAA that these are "amateurs" and "student-athletes" begins to sound rather hollow.
Over-signing allows a program to dole out more scholarships and cut ties with misses, but still on a relatively small scale. It's helpful, but it doesn't totally free a team from the limitations of only having 85 scholarship players when fall practice starts.
4) Encourage walk-ons
There can be no doubt that a major factor in the success of Tom Osborne's 90's Nebraska teams or of Bill Snyder's Kansas St teams are the huge role that their walk-on program has played.
Both teams consistently saw their rosters filled out with athletic, in-state players who weren't on scholarship from the football team (although you have wonder if boosters are at all involved in subsidizing the cost) but who's ranks frequently produce contributors.
Kansas St regularly finds contributors to their special teams, their 2-deep, and even their star ranks from the walk-on program. While the school doesn't recruit the top players in the nation every year, they do recruit to their system and they do acquire tons of walk-ons which makes them less vulnerable to the boom/bust cycle of speculating on the talent of high school boys.
However, schools like Kansas St and Nebraska probably have an easier pathway to building a robust walk-on program than a program like USC. If you are a solid player in a metro area, there are likely a lot of eyeballs on you and lots of scholarship options for you to take. USC isn't offering? Well why walk-on when you can play for free at Oregon, UCLA, or Boise St?
On the other hand, are you a rural kid who grew up loving Wisconsin but haven't been seen by many scouts, even in the Big 10? Perhaps you'd be willing to walk-on and earn a spot with the Badgers, fulfilling a lifelong dream. Especially if you still have some financial assistance in doing so...I'm not saying boosters cheat in this way, but I wouldn't be shocked.
Really the worst strategy to take, or at least the worst strategy anyone is likely to attempt, is to try and just take the best talent available in a given year at the expense of signing projects or playing walk-ons and hoping it will result in a cohesive team.
Do this, and you ensure that your program will be caught speculating on unworthy scholarship investments at some point and be subject to down seasons. Then, you just might lose your job. The government is not going to bail you out.