Robert Williams III sounded like he was progressing well, but his latest setback will keep him out more at least a couple weeks.

If any Celtics players believed Joe Mazzulla would mellow out now that he’s an NBA champion, they quickly discovered that was not the case. If anything, Boston’s eccentrically intense head coach is pushing his team even harder as it begins its bid for back-to-back titles.

But even for the Celtics players who have been with the team through the entirety of Mazzulla’s head coaching tenure, the opening day of practice brought some surprises. “If I could have told you exactly what was going to happen today,