Brown, 28, is a former seventh-round pick of the 49ers back in 2015. He was traded to the Patriots in 2018 in a pick swap.
Brown played out the final year of his four-year, $2.28 million contract before agreeing to a record four-year, $66 million deal that includes $36.75 million guaranteed with the Raiders in 2019.
Las Vegas traded Brown back to the Patriots this past March.
In 2021, Brown has appeared in one game for the Patriots.