Mark Cuban said that if the Mavs couldn't get DeAndre Jordan, they would have to consider tanking. Given that the Celtics have the Mav's 1st round pick (top 7 protected) for next year and that the Mavs roster isn't terrible, a tanking strategy could be really risky. The Mavs could easily end up with a number 7-10 pick, for example, that then automatically goes to the Celtics. That would be a totally wasted year.
Given that, here's a potential trade scenario that jump starts the Mavs rebuild and helps the Celtics:
Celtics get: Chandler Parsons
Mavs get: Jared Sullinger, James Young, Evan Turner the return of the Mav's 2016 pick, the Celtics 2016 and 2017 1st round picks.
Celtics Depth Chart:
C: Amir Johnson/Zeller
PF: David Lee/KO/Jerbeko
SF: Chandler Parsons/Crowder
SG: Avery Bradley/Rozier
PG: Marcus Smart/IT