Douglas had spent his entire six-year career with the Atlanta Falcons. He caught 51 passes for 556 yards and two touchdowns last season.
The 30-year-old Douglas had his most productive season in 2013, when he filled in for an injured Julio Jones and had career highs in starts (11), catches (85) and yards receiving (1,067).
Douglas originally joined the Falcons as a third-round draft pick out of Louisville in 2008.
AP NFL website: www.pro32.ap.org and www.twitter.com/AP-NFL