According to wikipedia:
"Tanking in sports refers to the practice of intentionally fielding non-competitive teams to take advantage of league rules that benefit losing teams"
I think you are riding a fine line with tanking versus rebuilding. I think you can tank while not asking coaches to lose games; simply give them players that they will not be able to win with.
Maybe Sabonis should just let his team play 4v5 on defense if he gives that kind of effort.