Just last year, the Spurs drafted Devin Vassell with their lottery pick, who plays the same role and position as Walker but is a much better defender.
Walker is not good enough to warrant the Spurs’ coaching staff starting him, and a bench role is probably best for Walker until he learns to be more consistent.
The Boston Celtics have multiple creators to help develop Walker, and they need a bench scoring option. If the Boston Celtics can exchange one of their younger players and draft capital for Walker, the benefits can go a long way.