Tatum is still the best prospect the Celtics have had since Larry bird.
Next season he will be the same age Pierce was when he entered the league.
He is not a better prospect than Paul Pierce (or Bird). He is the best prospect since Al Jefferson.
he's a better prospect than Pierce was. Pierce was still in College when he was Tatum's age. You can compare Tatum's stats next season to Pierce's rookie season to have a fair 1-for-1 comparison.
That's not to say that Tatum will end up as good as Pierce was in his prime (top 15 player/1 time 2nd team all-nba)... but if we're looking at Tatum as a prospect, his ceiling is higher than any player we've had since Larry Bird.