You just don't know what their ceiling is. They have young guys like Tatum, Rozier and Brown playing through the roof--better than expected. Horford has raised his game, and others are coming up with big games. It looks like they'll win the Philly series, and may face the Cavs again, who have surprised against the Raptors. The Cavs are the opposite of the Celtics--an aging team of veterans.
The Celtics, with their great coach, are capable of anything at this point. Nobody really knows what their ceiling is. Enjoy.