Flowers, 31, finished last season on injured reserve with the latest in a series of concussions, which led to concern about his future. The Chargers released Flowers in March, ending his three-year tenure with the team.
A second-round pick of the Chiefs in 2008, Flowers spent six seasons in Kansas City. He made the Pro Bowl in 2013 with a career-high 71 tackles, one interception and nine pass breakups.
He appeared in 119 games, with 117 starts, making 490 tackles, 21 interceptions and 111 pass breakups in nine NFL seasons.