I will repeat a little what I've said in another thread but, even if he is a damn good player, you had to wonder how much Spurs need to have Neal with their current roster.
Neal at PG isn't that good. He is way better at SG. If De Colo keeps playing that way, he might end up as the best option for the backup PG slot.
At SG, spurs still have Green and Ginobili. Even considering injuries and small ball, Neal would have a limited role as 3rd string SG.
Having a player that can bring instance offense at the end of the bench is always nice but Spurs do have another player with Mills that can play that role. Mills isn't as good as Neal but he is good enough for that role and he also bring some quickness that can be very useful in some matchups.