#14: Ausar Thompson
Thompson is also not untouchable, but he's shown enough for the Pistons to think he can and will be a big part of their future. The Pistons have lacked an elite defender on the wing since the Tayshaun Prince days, and Ausar has looked every bit the part of a guy who will make multiple All-Defensive teams and potentially compete for Defensive Player of the Year.
Could he be had in the right deal? Sure, if a superstar were coming back, but barring that, Thompson is going to be a Piston for the foreseeable future.
#13: Jalen Duren
Duren is barely 20 and already looks like one of the best centers in the Eastern Conference. He's a better passer than advertised, a great rebounder and his defense has improved, though he does still need a lot of work in that area. The only troubling thing with Duren so far has been his ankles, which he can't seem to stop spraining.
If the Pistons needed to include him to make a blockbuster deal, it's possible they would, but it's hard to imagine what that deal might be, so Duren is likely not going anywhere.