Rivers, 28, was signed to a two-year deal by the Bills in March 2014 after spending two seasons with the New York Giants. Rivers started three games and appeared in 12 for Buffalo, playing on 17 percent of the team's defensive snaps and recording 16 tackles.
Rivers was selected with the ninth pick of the 2008 draft by Cincinnati, where he collected 185 tackles, two sacks and two interceptions in 35 games over three seasons. In 27 games in two seasons with the Giants, he had 83 tackles and two fumble recoveries.
The Bills will save $1.7 million in 2015 salary cap money due to Rivers' departure.