Greivis Vasquez for Cory Joseph and Nando De Colo. Trade also includes a 2017 second rounder to Spurs.
Vasquez can play both guard spots and is a very good passer too. Mills is better than Cory and Nando at this point. If it doesn't work out Vasquez is a free agent. Toronto would get one of it's own plus Nando could beef up their guard position as well. Works on both ends. Raptors have two second rounders in 2017 and the Spurs would get the lesser value of the two.