Chill out. There´s a sweep-to-be in the Finals going on, featuring a team with all its stars in their 20s. Nobody, absolutely nobody, is going to give picks away for established stars, except possibly Cleveland or San Antonio, and neither have any decent picks to trade away.
While it´s almost certain that Boston will take Markelle, the operating word here is “almost”. If Markelle were still available at 5, it´d be because the other 4 teams ahead of you have seen a massive red flag of some sort, and you don´t want to have to take the gamble without having worked the kid out yourself. Due diligence, nothing more dramatic than that.