Everything's in here:
http://www.celticshub.com/2017/07/05/gordon-hayward-sign-trade-options/
The ideas in this article make more sense than what the announcers were discussing during the Spurs game. They were thinking we might give Marcus to Utah in the sign and trade, taking back nothing but Hayward and cap room. I read one article talking about sending Jae to Utah in a similar deal.
(1) Yuck. It's hard to believe that those deals are the best we can do... (2) I thought salaries had to be within 25% in a trade, but maybe there are some details I'm not following. TPEs have to come from somewhere, and maybe this is where???