"Free up flexibility" = Green, Bass, or Wallace trade.
Maybe Cleveland was willing to take on Green if the Deng trade had fallen through. Green could still be desired by a few desperate teams that need scoring punch, especially now that his contract has elapsed another year. However, I don't see anybody giving up anything great for him.
I can see some team being interested in Bass as a low cost one-year free agent but a first rounder would be too much for him. Boston would probably have to settle for a 2nd rounder, which means they may just keep him. Of course, he could also be combined with Anthony to make a deal for a high-priced player this summer.
Wallace is most likely still not going anywhere unless the Celts give up an asset.