Caldwell, 31, is a former third-round pick of the Bengals back in 2008. He played out his rookie contract with Cincinnati before signing on with the Broncos as an unrestricted free agent back in 2012.
Caldwell had spent the past four season in Denver before signing a one-year contract with the Lions back in May. Detroit placed Caldwell on injured reserve with a hand injury during the preseason before later releasing him with an injury settlement.
In 2015, Caldwell appeared in 14 games for the Broncos and recorded 10 receptions for 72 yards receiving and two touchdowns. Pro Football Focus has him rated as the No. 106 receiver out of 121 qualifying players.