Our sister network ESPN is reporting that Brown is facing a suspension over a confrontation Wednesday with General manager Mike Mayock.
Reports say the incident involved Brown's posting of a letter from Mayock on social media, informing the receiver that he had been fined.
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Brown was not at practice on Thursday.
Neither Mayock nor Coach Jon Gruden is saying why.
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If suspended, the Raiders could void $29 million in guarantees in Brown's contract he signed earlier this year.
It's been a tumultuous pre-season for the 31-year old, from a case of frostbitten feet, to a confrontation with the NFL over his helmet.
ESPN has contributed to this report.
The Next Chapter: Antonio Brown and GM Mike Mayock got into it Wednesday, and the team is now planning to suspend its star wide receiver, league sources tell ESPN.— Adam Schefter (@AdamSchefter) September 5, 2019
Antonio Brown posted the fine letter on social media that Raiders’ GM Mike Mayock sent him. It led to an exchange, which is now leading to further discipline. This is not going away anytime soon.— Adam Schefter (@AdamSchefter) September 5, 2019