At this point, the Bucks should be sending back draft picks. He's been that bad.
* He's averaging 6.7 points per game. That's really bad, but is the second highest total of his four-year career;
* He's shooting 43.3% from the field, which is atrocious for a guy of his size and athleticism. An anomaly? Nope. He's shot below 46% in three out of his four seasons. He's been a terrible FT shooter, too;
* He's got character issues, both in public and in the locker room;
* He's vastly overpaid starting next year ($44 million over four years);
* He's overrated as a defender, and can't stay out of foul trouble (5.0 PF per 36 minutes).
I've called this guy "Javale McGee 2.0", but that's probably vastly unfair to Javale. It just doesn't make sense to give up draft picks for the pleasure of having Sanders take up 20% of your salary cap for the next four seasons.
As crazy as it is to say, I'm not even sure if I'd do Wallace + a #2 for Sanders. You probably have to, I guess, for the potential. However, between Sanders' attitude, offensive ineptitude, and terrible contract (again, a year longer than Wallace's), I'd be very hesitant.