If you thought the Antonio Brown helmet controversy was over, well, you might want to think again.

After Brown missed another practice on Sunday while protesting the league's helmet policy that has prevented the wide receiver from wearing the same type of helmet that he's worn his entire career, Mike Mayock met with the the media on Sunday to discuss Brown's absence. The GM didn't waste time or pull punches, delivering a rather emphatic message to the missing wide receiver. 

"You all know that A.B. is not here today. So here's the bottom line. He's pretty upset about the helmet issue," Mayock said. "We have supported that. We appreciate that. But at this point, we've pretty much exhausted all avenues of relief. So from our perspective, it's time for him to be all in or all out. So we're hoping he's back soon."

On Saturday, days after the star wide receiver was back on the field with the Oakland Raiders, warming up ahead of the team's second preseason game with a new helmet following an unsuccessful attempt to gain NFL approval for his old, now-banned head-wear, Brown has apparently encountered another helmet hurdle in the lead-up to his 2019 season.

ProFootballTalk's Mike Florio reported Saturday that the NFL recently reversed course on its promise to allow Brown to wear a Schutt AiR Advantage helmet as long as he could find one less than 10 years old. In doing so, per Florio, the league decided to require testing of Brown's new helmet, which was made in 2014 and had been certified for use by the National Operating Committee on Standards for Athletic Equipment (NOCSAE). And after recently examining it, the NFL informed Brown that his helmet failed the test.

Florio added that "we haven't heard the last of Brown on this issue" -- hours before the receiver used graphic language to slam the NFL over Twitter

Brown's original style of helmet, PFT noted, was not among 11 different models that became prohibited this season, but Brown was not permitted to wear his traditional model because it was more than 10 years old.

It remains to be seen if -- and for how long -- this latest ordeal could keep Brown away from the practice field. The former Pittsburgh Steelers star was set to begin full participation at Raiders camp, according to coach Jon Gruden, who told the media Saturday that Brown was a full go at Oakland's most recent walk-throughs after recovering from frostbitten feet. The Pro Bowl pass catcher previously denied rumors that he was considering retirement over his ongoing issues with helmets.