The Celtics walked into Madison Square Garden and benched their top six guys because of a weird and stupid preseason back-to-back (and part of a three-in-four stretch), turning the Monday night game against the Knicks into less of a dress rehearsal between division rivals and more of an audition for Boston’s supporting cast. It’s like Boston’s top six guys were the cast of Friends and the rest of the guys spent Monday night reading for Gunther, Janice, Mike, and Richard.