Tatum has quickly become the #3 guy on the Celtics' totem pole, after Irving and Horford. Remarkable for a 19 yo kid. Just watched the replay of that Hawks game on NFL network. His key corner 3 pointer at the end sealed it.
I don't know if Hayward would be much better at this point. The kid shows remarkable maturity on the court, and can shoot the eyes off the ball. He has superstar potential.