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Oakland Raiders receiver Antonio Brown reportedly warned the NFL he would hold the league liable if he suffers a head injury while wearing a new mandated helmet.

"And I think it'll be interesting if the NFL forces Antonio to wear a different helmet," a source told Daniel Kaplan of The Athletic. "And he does play and he doesn't retire as some people have reported he will do. And then he suffers a really severe injury. I'd hate to be the NFL. Because now you've forced him into wearing a different type of helmet. And I think at that point, though, the liability will be dramatic."

The NFL banned Brown from using his 12-year-old Schutt Air Advantage helmet beginning this season as part of new safety precautions. Thirty-two players wore helmets last season that would be banned under 2019 rules, and Brown appears to be the only one who is not complying.

Brown has threatened to retire if he is not allowed to wear his old helmet, per ESPN's Adam Schefter. He has been absent from team facilities amid the drama while also dealing with frostbite in his feet after not using proper protection in a cryotherapy chamber.

Brown has been using the same helmet his entire career. In his grievance, Brown argues that the NFL never tested his helmet and therefore should not be able to ban it. The league bars players from using equipment that is not certified by the National Operating Committee for Standards and Athletic Equipment. The NOCSAE stops testing equipment that is over 10 years old, while Brown's Schutt helmet is 12 years old.

Brown's helmet was previously certified in 2008.

The seven-time Pro Bowler is coming off his sixth straight 100-catch season, an NFL record, but has been enveloped in controversy all offseason. The issues began when he forced his way out of Pittsburgh by criticizing quarterback Ben Roethlisberger, coach Mike Tomlin and team management—doing so via social media and national television appearances.

After being traded to Oakland, the helmet issue began cropping up during OTAs, and he's barely practiced since training camp began. The NFL could rule on Brown's grievance as soon as next week, but his future is in the balance in the meantime.