I think only Anderson will eliminate himself out. He will get chances to prove himself and also will be coached to improve. Spurs did not get a true backup SF other than him. Simmons can defend but his game and size is more of a SG. He is closer to 6'4 barefoot than 6'5 and does not have lengthy arms. Spurs played him in SL and in the D'league as a SG and sometimes as a PG (when Cotton was picked up by the Jazz), never as a SF. That was revealing to me. If the Spurs picked up a backup SF it would have to be a veteran that would not mind losing minutes to Anderson. If he breaks out like the Spurs hope he will, that vet will not play. It is one of the main reasons I think the Spurs were unable to pick up a backup SF in the vet bargain bin market.
Nobody wants to look at that aspect, but Anderson has improved and played really well. Rookies are known to struggle in their first year just in a general sense, not just him. Its likely he will be much better this year, and if he is, whoever else is in the 5th or a 6th wing has to be okay with that. Simmons is versatile and you can play him together with Anderson when Manu sits which makes it an even better fit in this roster. But make no mistake, Anderson will play.