Basically, the Spurs have been shopping Blair for quite some time. With Tiago Splitter looking like a permanent fixture next to Tim Duncan in the frontcourt, Blair has largely dropped out of the rotation, even though Gregg Popovich distributes his regular season minutes like a youth league coach.
The puzzling thing to me is that Blair has made the most of his minutes when he's in there. Any time I see him play, he generally provides a nice spark once he gets in the game. For whatever reason, San Antonio seems to just want him gone.
As far as possible destinations, HoopsWorld says a deal with the Miami Heat fell through.
I hope he gets a trade, but even if he doesn't, it won't be the end of the world. He's an unrestricted free agent after this year and will get to pick his next destination. And trust me - there will be suitors for him interested in his services. He's a young big man that has already had some success in the NBA. Even if he doesn't get a starting job, there will be any number of teams interested in him as a backup.