It was a worrisome time for the Celtics, who were put into self-quarantine when they arrived back to Boston from their trip to Milwaukee, but they had all the confidence in the world that Smart would beat COVID-19. He is, after all, Marcus Smart, Boston’s defensive bulldog who doesn’t back down from anything. “Marcus is just a great guy with a huge heart. I think COVID took a look at him and said ‘to heck with it,’” Celtics owner Wyc Grousbeck joked during an interview with WBZ-TV’s Dan Roche. “He’s so strong. Not to make a joke of it, but we’re glad he’s back and he’s fine. Everyone is working out and shooting baskets and hopefully we can unlock basketball soon enough.”