Starting Quarterback Trent Edwards #5 of the Buffalo Bills suffers a concussion after getting hit by Strong Safety Adrian Wilson #24 of the Arizona Cardinals during the first half of their NFL Game on Oct. 5, 2008 at Stadium in Glendale, Arizona. Photograph by Donald Miralle/Getty Images
Starting Quarterback Trent Edwards #5 of the Buffalo Bills suffers a concussion after getting hit by Strong Safety Adrian Wilson #24 of the Arizona Cardinals during the first half of their NFL Game on Oct. 5, 2008 at Stadium in Glendale, Arizona. Photograph by Donald Miralle/Getty Images

The NFL's concussion settlement with a group of retired players hit a snag today, when a federal judge denied preliminary approval of the deal because of issues with compensation sufficiency and fairness.

The crux of the proposed $765 million settlement is a $675 million fund to compensate players diagnosed with various diseases related to head trauma, such as Parkinson's and ALS, with varying payout amounts based on the severity of the disease. It also includes $75 million for a baseline assessment program that would conduct neurological evaluations of retired players to determine the presence of such diseases, a $10 million education fund to promote safety in professional and youth football, $4 million in notice expenses, and a provision requiring the NFL to cover the players' attorney fees in a separate payment of up to $112.5 million.

In her order denying the motion, Judge Anita B. Brody expressed concern that the settlement would not adequately cover the thousands of former players involved in the class-action suit once all the evaluations and diagnoses are conducted. She explains:

The Settlement contemplates a $675 million Monetary Award Fund with a 65-year lifespan for a Settlement Class of approximately 20,000 people. Retired NFL Football Players with a Qualifying Diagnosis of Parkinson’s Disease, for example, are eligible for a maximum award of $3.5 million; those with a Qualifying Diagnosis of ALS may receive up to $5 million. Even if only 10 percent of Retired NFL Football Players eventually receive a Qualifying Diagnosis, it is difficult to see how the Monetary Award Fund would have the funds available over its lifespan to pay all claimants at these significant award level.

It's an understandable concern, with recent data shedding light on the prevalence of brain damage in former NFL players. In September 2012, a long-running study found that 334 of 3,400 retired players (9.8 percent) died from cognitive disease in the test period -- about three times the rate for average American men and close to the hypothetical 10 percent figure Brody uses in her ruling.

Despite the assertions by the players' attorneys that the agreed-upon figure was arrived at after lengthy analyses by independent economists and would be enough to cover all eligible plaintiffs, these analyses were not provided to the judge, who said that she required documented proof of the settlement's sufficiency.

The NFL, in a statement, said it respected "Judge Brody’s request for additional information as a step towards preliminary approval. We will work with the plaintiffs' attorneys to supply that information promptly to the court and special master. We are confident that the settlement is fair and adequate, and look forward to demonstrating that to the court."

The proposed settlement had already been criticized as a slap on the wrist for the $9 billion league, and sparked outrage by excluding the families of players who died before 2006. Although this ruling won't help solve the latter issue, it will probably force the NFL to fork up more money, meaning there's at least one judge who's not afraid to stand up to the shield.

(Kavitha A. Davidson is a Bloomberg View columnist who writes about sports. Follow her on Twitter at @kavithadavidson.)