They had one on a very manageable long term contract in Finney-Smith and included him in the package for Kyrie. DFS is not perfect but as a complimentary piece next to Luka he’s just about perfect.3 and D players are the most in demand ones, it's the most difficult thing to provide.
Coincidentally Nets are full of players exactly in the mould of what Mavs should be after. Bridges, Johnson, DFS and Claxton would be sublime next to Luka.