Raiders WR Antonio Brown not practicing, general manager Mike Mayock says

Antonio Brown warms up before the NFL preseason game against the Arizona Cardinals at State Farm Stadium on August 15.

(CNN)Antonio Brown finally has a helmet, but it appears his troubles are not over.

The Oakland Raiders wide receiver was not at the team facility on Thursday, general manager Mike Mayock told reporters. The team did not say why or if he was being disciplined.
"Antonio Brown is not in the building today," Mayock said. "He won't be practicing. I don't have any more information for you right now. And when I have some, and it becomes appropriate, you guys will all get it, I promise you. But that's it for today."
The Raiders' injury report shows that Brown did not participate in practice Thursday with the description as: "Not injury related - conduct."
    Brown took to Instagram Wednesday, posting a letter purportedly from Mayock informing him he has been fined close to $54,000 by the team for missing time during preseason training camp.