On Monday, the family of late Buffalo Bills fullback Carlton “Cookie” Gilchrist filed an appeal with the U.S. Supreme Court to review the case involving NFL players diagnosed with the degenerative brain disease known as chronic traumatic encephalopathy (CTE), The Washington Post reported.

The move by Gilchrist’s family, which came in just under the Court’s appeal deadline, throws a monkey wrench in the $1 billion class action settlement deal between the NFL and more than 5,000 former players involved with the case. Scott Gilchrist said it was “irrational that a federal judge in Philadelphia excluded future payouts for CTE from the potential $1 billion settlement, though the science continues to develop,” the Post reported.

The players originally settled with the league about three years ago before a federal judge finalized their agreement in March, according to the New York Times. The terms of the settlement permit more than 21,000 former NFL players to receive up to $5 million of the $1 billion settlement funds for up to 65 years of their lives, the Post reported.

If Gilchrist’s family had let the deadline pass, as other players and their attorneys intended to do, the first payment would have been issued about three months after the “effective date.” Now payouts could be delayed for several months.

The other players’ decision not to appeal the case centered largely on the fact it would prolong their fight with the NFL, as well as the settlement funds and medical benefits many retired players need as soon as possible.

Chris Seeger, co-lead counsel for the retired players, told Fortune he was disappointed with the Gilchrist family’s last minute decision to appeal.

“The Supreme Court should deny the appellants’ petition, as these objections have now been exhaustively examined and overruled by both the district court and the third circuit,” Seeger said in an email. “These appeals come with devastating consequences for the thousands of retired NFL players suffering from neurocognitive injuries, and effectively stand between truly injured retired players and their sole prospect for obtaining benefits while still alive… it is clear the few lawyers still objecting to this settlement have motives other than what is in the best interest of the retired NFL player community.”

The NFL first agreed to settle with former players after high-profile studies came out about the effects of playing pro football. Research revealed that players who sustained repeated blows to the head faced an increased risk of long-term neurological health problems, including CTE, according to the Times.

League officials long denied there was a direct correlation between playing pro football and CTE. Then in March, a league official conceded there was in fact a link between the two, the Times reported.

Fortune has reached out to the NFL and will update this story if it responds.