ESPNDallas.com's Tim MacMahon reported that Lamb's contract does not include any guaranteed money.
Lamb, a 6-foot-4, 200 pound shooting guard, is entering his third season in the league. In 100 career games with the Milwaukee Bucks and Orlando Magic, he has averaged 3.5 points and one rebound in 12.7 minutes per game.
The Bucks selected Lamb in the second round of the 2012 draft after he played two seasons at Kentucky.
The Mavericks finished last season 49-33 and 8th in the Western Conference.