The report comes after Boldin announced his retirement on Aug. 20. The announcement came "less than two weeks after signing a one-year deal with the Bills" because Boldin was "leaving football to focus on social activism," per ESPN.com.
According to the report, the letter pointed to Boldin's desire to play close to his Florida home and family, although the Bills will have final say on any potential trade. Considering the trade deadline is Tuesday, Boldin and his agent don't have much time to explore the market.
Boldin has three Pro Bowl appearances and a Super Bowl title with the Baltimore Ravens on his resume.
While he is 37 years old and hasn't played a game this season, he tallied eight touchdown catches last year as a member of the Detroit Lions and surpassed the 1,000-yard mark two straight seasons in 2013 and 2014 with the San Francisco 49ers.
Boldin has played 14 seasons with the Arizona Cardinals, Ravens, 49ers and Lions throughout his impressive career and has 82 total touchdown catches and seven different years of more than 1,000 receiving yards.