Seriously? You don't do it because it's just not done. If this gets started, if s up the whole offseason process. Nobody can count on any agreement during this part of the offseason. Teams don't know if they can quit pursuing other players. , players don't know if they have a deal - a team could swing another player cheaper. The Players Union would have a ing fit if that happened.
I guarantee you, the Spurs FO would refuse to talk to a player who pulled something like this. Because they would understand that there have to be some rules, or everyone is screwed. It's worse than classless.