Antonio Brown's camp reportedly believes the wide receiver has been treated unfairly by the NFL. (Rick Scuteri/AP)

It turns out that Antonio Brown’s helmet saga has not quite run its course. However, the Oakland Raiders appear to have run out of patience with their star wide receiver, who skipped training camp Sunday.

“It’s time for him to be all-in or all-out,” Raiders General Manager Mike Mayock said of Brown to reporters. Oakland then emphasized Mayock’s message by posting his comments on the team’s official Twitter account.

Brown initially was absent from Raiders camp because his feet were frostbitten after a cryotherapy session. Then he threatened to retire because the league deemed his preferred helmet, a Schutt AiR Advantage, illegal. The only helmet he had worn in his first nine seasons, it was phased out under a safety policy enacted by the NFL and its players’ union.

After Brown lost a grievance hearing, he appeared to have found a loophole in which he could continue to wear his helmet if he could find versions of it less than 10 years old. He was able to round up a few and returned to training camp Tuesday. “Been dealing with a lot of adversity,” he said then. “I’m excited to be back, see my teammates and get in the groove of things.”

According to a report Saturday by Pro Football Talk, the NFL then found its own version of the Schutt helmet, from 2011, and administered a test that the equipment failed.

“Brown’s camp now believes that the NFL rushed to test the Schutt AiR Advantage specifically to keep Brown from wearing it,” Pro Football Talk reported, “without the grace period that others (such as Patriots quarterback Tom Brady) were able to utilize before permanently ditching their helmets.”

In a reply to a tweet Saturday from the website about its helmet scoop, Brown exclaimed on his official account, “Super Prejudice unbelievable!”

On Sunday, Brown missed the Raiders’ morning walk-through and afternoon practice.

“You all know that AB is not here today,” Mayock told reporters at the Raiders’ Napa Valley training facility. “So here’s the bottom line: He’s upset about the helmet issue — 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.

“We’re hoping he’s back soon. We’ve got 89 guys busting their tails. We are really excited about where this franchise is going, and we hope AB’s going to be a big part of it, starting in Week 1 against Denver. End of story, no questions.”

The Raiders had suggested a day earlier that Brown might be able to participate in his first practice Sunday. The seven-time Pro Bowler, who was acquired in March in a trade with the Pittsburgh Steelers, impressed his new team during a walk-through Saturday.

“The man’s recall is unbelievable,” quarterback Derek Carr said (via ESPN). “He came in and no mental errors, and in this offense, that’s not easy to do. … You can tell Antonio’s been studying because he came out and didn’t miss a beat. He was a part of everything we did today.”

While denying a report Thursday that he might retire if he could not wear the Schutt helmet, Brown said he felt “misunderstood,” adding: “I’m not here to try to win people over or make people feel a certain way about me. I’m an athlete. I’m a human being. I’ve got tough skin. Just treat me like a human. Treat me with respect. But through it all, I’ve got a strong heart. ...

“Why would I retire? I’ve got a beautiful career. I’m healthy. I love to play the game. Obviously, I inspire people with the way I play the game. I’m grateful to play, and I’m excited to put on this uniform.”

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