Celtics guard Marcus Smart had a brief-but-animated flare-up with assistant coaches on the Boston bench late in the fourth quarter of Tuesday night's 123-108 loss to the Wizards and was sent to the locker room before the end of the game. Smart, who had played 17 of the first 20 minutes of the second half, subbed out with just under four minutes remaining and the Celtics trailing by 13. A little more than a minute later, he started to walk toward the scorer's table to check back in, but coach Brad Stevens immediately followed him. On the court, a turnover triggered the final TV timeout of the game. Smart returned to the bench at that point and sat down in the huddle as if he was re-entering the game. Some of Boston's assistant coaches attempted to remove him, but Smart was shown on the television broadcast having a heated exchange with assistants Jerome Allen and Jamie Young, which included waving a towel in their direction as Stevens sat in front of the...