Jeff Green wears a mask of solemn, self-imposed pressure that he rarely lifts in public.

He’s the best dunker on the Celtics, and a particularly riveting athletic play can crack through the deadpan. On some nights he will carry a game — every NBA player’s dream — and maybe then a relieved smile will light up the arena.

Then comes a moment like Wednesday night in Indianapolis, when all inhibition melts. About three seconds remained when the Celtics forward broke free off a pick by teammate Paul Pierce, reached high for a Kevin Garnett bullet pass, and laid in the game-winner in the Celtics’ 83-81 victory over one of the hottest teams in the Eastern Conference.

Green and Garnett charged at each other as if they had just won the NCAA championship. They collided in a kind of slam hug, and started a wild Celtics celebration out by the foul line. By the time Green met the media — a process he tolerates more than enjoys — the mask was back on. It’s his shield.

Save for fellow heart-surgery patient Chris Wilcox, no NBA player has weathered more during the last year. The surgical scar that splits Green’s chest like the mountain range on a relief map — the scar he’ll sometimes tap as a reminder of his climb back into the league — defines his challenges.