Pittsburgh isn't going to simply give away a talent like the wide receiver.
49ers head coach Kyle Shanahan was asked about his team's interest in Brown during the week leading to the Senior Bowl in January.
ESPN's Adam Schefter reports that the star wide receiver has formally requested a trade.
Brown appeared to make his decision official in a social media post released on Instagram on Tuesday.
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He's under contract for three more years, and the Steelers have shown no inclination to cut him, if they can't trade him.
Brown has been with Pittsburgh his entire career but his relationship with the team has soured over the past year.
Brown will not become a free agent until 2022 under his current contract with the Steelers, although trade talks have circulated heavily since the end of the 2018-19 National Football League season.
Brown is a seven-time Pro Bowler and has been named to the NFL's All Pro first-team four times. He also pleaded guilty to a reckless driving charge on Tuesday in Pittsburgh, stemming from a November incident when he was caught driving at more than 100 miles per hour. The woman did not press charges and Brown was not arrested.
It also came out that Brown was hit was hit with two lawsuits in October for an incident that allegedly occured at his South Florida high-rise last April.