10. Philadelphia 76ers
Even though the Philadelphia 76ers are still projected to finish as a Play-In Tournament team in the Eastern Conference, I can't help but think that this could end up being the most dangerous threat to the Boston Celtics heading into the NBA Playoffs. With the Cleveland Cavaliers fading and the Milwaukee Bucks and New York Knicks dealing with their injury woes, the Sixers could be trending upward at just the right time. Joel Embiid is back and while he may not be in MVP form just yet, he's looked good enough.
And if the Sixers can remain healthy throughout this postseason run, there's no doubt that they could compete with any team in the East. At this point, with how the East bracket looks, the Sixers could very much find themselves in the Eastern Conference Finals (assuming they avoid the Celtics in the first round).
Whether the rest of the conference is willing to admit it or not, the Sixers might be the biggest threat to spoil the Celtics' historic season.