In a move that could have major repercussions on the future of the National Football League, a federal judge in Philadelphia has denied preliminary approval to a proposed class-action settlement between the NFL  and retired players, who sued the league over concussion-related claims.

In her opinion released Tuesday, U.S. District Judge Anita Brody raised concerns that the $675 million the NFL agreed to set aside might be inadequate to cover claims from roughly 20,000 eligible former players, family members and their representatives.

Brody requested that both sides provide her with more information on how they arrived at that figure.

The ruling comes a week after lawyers for the retired players and the NFL released a detailed look at how the total $760 million settlement would be distributed.