There are no fewer than five major pending legal challenges against the NCAA and college conferences, covering the gamut of issues. Player pay, scholarship amounts, player health, and the entire basis of amateurism are at stake in lawsuits across the country.

But which cases have the legs to run the full course and actually change how college sports operate? We've assigned each a rating on a scale from 1 to 10, from least to most likely to entirely change the NCAA. A threat level, if you will.

The premise: Former Northwestern quarterback Kain Colter and a group of other Wildcat football players created the College Athletes Players Association this winter and petitioned the National Labor Relations Board for union status. A seal of approval from the NLRB would allow the players collective bargaining rights under federal labor law. Players could negotiate salary and benefits with their schools, conferences, or the NCAA.

The status: The regional NLRB in Chicago heard the Northwestern case in February. Colter essentially argued that he was a professional football player for Northwestern, and that his education was a secondary concern. Northwestern countered with ample evidence to show that it takes academics seriously, an argument that could have began and ended with, "We're Northwestern." The NLRB decision is still pending.

More: Northwestern both the best and worst battle ground

The odds: Low. For one, the NLRB's decision will have no effect on state schools, as public institutions are not governed by the Board. For another, the NLRB's decision would be appealed to the national board regardless of the decision. The final arbiter, which could technically be the Supreme Court, would have to find that players are university employees, a contention that flies in the face of the language of the letter of intent.

The union idea could be used to advance some positives -- better postgraduate healthcare, for one -- but it's unlikely to make a serious dent.

RATING: 2.0/10.0

The premise: Athletes got concussions and the NCAA didn't do anything about it. Those players now have medical problems and need some help.

The status: The first NCAA concussion case was brought by Adrian Arrington, a former defensive back and rover for Eastern Illinois, in 2011. Since then, players from across the country have filed their own cases, and not just in football; hockey players and women's soccer players have also filed.

In January, attorneys for the former players and NCAA agreed to unite the cases in one court, in order to prevent different results across jurisdictions and centralize the settlement process. Much like with the NFL's concussion litigation, it is expected that the parties will wait until all potential plaintiffs get into the case, then settle.

The odds: There's little doubt that the NCAA faces some liability here. In a 2010 email, an NCAA government relations officer asked the organization's top health and safety official whether concussion recommendations in youth sports exceeded those of college sports. The health officer replied, "Well since we don't currently require anything all steps are higher than ours." That's not good.

With that said, the issue -- player health -- is far less controversial than the underpinnings of amateurism, and the potential class of athletes is much smaller. So, as with the union case, progress toward player safety wouldn't necessarily crumble the NCAA.

RATING: 4.0/10.0

The Shawne Alston case

The premise: Alston, a former West Virginia football player, filed suit against the NCAA and five major conferences in early March, alleging that the schools have violated antitrust laws by limiting an athletic scholarship below the "full cost of attendance." Alston, who is represented by two lawyers who have been involved in the O'Bannon case, says he was forced to take out additional loans to cover the cost of attending West Virginia while his coach made in excess of $3 million a year.

The antitrust claim arises from the fact that every university uses the same basic scholarship formula and will not increase it to meet the cost of attendance, which looks a lot like collusion to keep costs down.

The status: The suit was just filed, so we have a long way to go.

The odds: Fairly high. Former Oklahoma quarterback Jason White filed essentially the same suit against the NCAA in 2006, a case that settled for $10 million two years later. But $10 million isn't a game-changer for just about any AQ-conference school, let alone the NCAA.

The case could be resolved by the NCAA simply agreeing to allow for full cost of attendance scholarships going forward and setting aside funds to help former players pay off loans and debts. The increase in scholarship amount has been floated by Big Ten commissioner Jim Delany and supported by other large conferences, though mid-majors and FCS conferences have objected that it will drive their costs too high. If Alston's suit leads to a resolution of that conflict, he and his lawyers will likely be happy.

RATING: 6.0/10.0

The Jeffrey Kessler antitrust case

The premise: Where other lawsuits nibble at the edges of the NCAA's rules and regulations, this one strikes straight at the heart of the matter.

Jeffrey Kessler, a famous New York antitrust attorney, filed a class action antitrust suit earlier this week against the NCAA and five major conferences. Kessler is not seeking damages, but rather an injunction that would prevent the NCAA and conferences from limiting the amount of financial aid that can be given to an athlete. He alleges that the NCAA, Big Ten, Big 12, SEC, ACC, and Pac-12 have colluded to fix the price of players.

The status: Again, it is just filed.

The odds: This isn't a new concept. The White suit alleged essentially the same thing, and Alston is making a similar claim now.

Kessler is not out to make money. He's trying to blow up the entire system.

The NCAA has even been previously found to violate antitrust. laws. In a 1984 case, the University of Oklahoma alleged antitrust violations by the NCAA with regard to television broadcast rules that prohibited a football program from appearing on television too often. When Oklahoma showed up on TV more than the rule allowed, it was cited by the NCAA, leading Oklahoma to file suit. The NCAA lost, leading to the deregulation of television rights.

That deregulation is what has led to the absurd amounts of television money filling the coffers of universities across the country today, the millions of dollars that players are now trying to get.

Where it is different is the remedy. Kessler is not out to make money. He's trying to blow up the entire system. The fact that he (and his plaintiffs) are not seeking damages mean that a simple settlement from the NCAA and conferences does not look immediately feasible, because Kessler isn't interesting in a pile of cash. He has the resources and clout to make it happen, too.

There are problems, though, beginning with the fact that equitable remedies such as those requested by Kessler are not available when monetary damages can suffice. Kessler will have to establish that the proverbial bag of cash would be insufficient to fix the problem, a proof that could be difficult given the result of previous cases. Still, Kessler's resources and expertise make this the best credible threat to the NCAA's system outside of Ed O'Bannon.

RATING: 7.5/10.0

The premise: Initially brought as a case against the NCAA, EA Sports, and the Collegiate Licensing Company for the improper use of player likenesses in EA's NCAA-related video games, the O'Bannon suit has morphed into an attack on the source of the NCAA's largesse: Television revenues. A group of former and current football and basketball players is asking that a portion of television revenues be put aside to go to players, since it is those players' likenesses that are making the television rights so lucrative.

The status: After years of litigation and myriad challenges from both teams of attorneys, U.S. District Court Judge Claudia Wilken rejected the final challenges to the suit in February and forced the parties into settlement talks in March. Attorneys for the players have indicated that the settlement negotiations could involve more issues than just the likeness question at the heart of the case, including player pay and scholarship limitations.

Trial is set to start June 9.

The odds: If the plaintiffs get their way, it could be financially catastrophic for the NCAA. The exact structure of a win for the players isn't quite clear, but it likely would involve a considerable payment to a fund that would pay players after they exhausted their eligibility.

Some athletic directors have said it would bust their budgets and force them to cancel non-revenue sports, a claim that rings somewhat hollow for programs that were sponsoring gymnastics and rowing long before the conferences got their own networks.

With that said, Judge Wilken has appeared equally skeptical of the parties throughout the case, and could well find that the pursuit of television revenues is a bridge too far. If so, an already-accepted settlement of the video game claims will have to suffice.

RATING: 8.0/10.0