I don't think they move Darius unless it's in a deal that gets a high level starter under contract with some years left who plays the 3 along with a stop-gap-level PG.
Cavs aren't looking to add more unscratched scratch-off tickets for one of their top 3 to 4 assets.
Would you trade Garland/Cedi (filler like Brodric. Wade and Kabengele) to the Spurs for Vassel and White? Add shooting, White has 4 years left on his deal, Vassel is a legit 3-D prospect. Problem is White is only a solid player and is more a 2 than a 1 but he has the right size to pair with Collin, and Vassel is unproven. Maybe it's Dejounte Murray instead of White, but then you have some shooting issues, maybe you try and include Primo? DOn't know that the Spurs have a trade to be had here.. but that's the kind of framework: proven young-ish player under contract and another player that fits need/timeline.
Anyway, Garland to GS makes no sense for GS, Garland to Toronto for Barnes, no thanks (maybe for OG, but Toronto doesn't do it).