ALAMEDA, Calif. — Star receiver Antonio Brown said Wednesday that the Oakland Raiders have fined him close to $54,000 for missing a practice and walkthrough last month.

Brown posted a letter on his Instagram account from general manager Mike Mayock saying that he was fined $40,000 for an unexcused absence from practice on Aug. 18 and $13,950 for skipping a walkthrough in Winnipeg on Aug. 22.

Brown also wrote on the account: "WHEN YOUR OWN TEAM WANT TO HATE BUT THERE'S NO STOPPING ME NOW DEVIL IS A LIE. EVERYONE GOT TO PAY THIS YEAR SO WE CLEAR."

Mayock had given Brown a public ultimatum following the missed practice to be "all in or all out." Coach Jon Gruden said after Brown returned to the team two days later that Brown was "all in," but he then missed the walkthrough in Winnipeg.

"Please be advised that should you continue to miss mandatory team activities, including practices and games, the Raiders reserve the right to impose additional remedies available under the Clubs Discipline Schedule, the CBA and your NFL Player Contract, including, but not limited to, additional fines and discipline for engaging in Conduct Detrimental to the Club," Mayock wrote in the letter.

Brown has had an eventful first season with the Raiders before even playing a game. He arrived at camp with the frostbitten feet, sending him to the non-football injury list. He was activated on July 28 and participated in parts of two practices before leaving for more than a week to get treatment on his feet.

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He also was in a fight with the NFL and NFLPA over what helmet he could use. The league and union no longer allow the helmet Brown has worn his entire career over safety concerns. Brown filed two grievances hoping to be able to use his preferred helmet but lost both of them and has found a new one he has deemed suitable.

Brown had 686 catches and 9,145 yards receiving the past six seasons in Pittsburgh, the best marks ever for a receiver in a six-year span. But he still wore out his welcome with the Steelers after leaving the team before a crucial Week 17 game last season, and Oakland was able to acquire him in March for the small price of third- and fifth-round draft picks.

The drama that surrounded Brown in Pittsburgh didn't stop upon his arrival in Oakland even though he was given a hefty raise with a three-year contract worth $50.125 million.