No team ever in the NBA has come back from a 3-0 playoff deficit. The last time that happened in any major sport was (who else)the 2004 Boston Red Sox. Those bunch of idiots beat the Yankees four games in a row and later went on to win the world series. Cowboy Up!
"Don't let us win tonight. This is a big game. They've got to win because if we win we've got Petie coming back today and then Schilling will pitch Game 6 and then you can take that fraud stuff and put it to bed. Don't let the Sox win this game." Those were the words of leader Kevin Millar after the 3-0 deficit for the Red Sox.
Apparently, Doc Rivers repeated Millar's quote before the game to his team. There are no better teams to come back from insurmountable leads than the Boston teams, especially the Celtics. If the Celtics lose this series, the "Big Three" era will likely end. KG will probably foul and Pierce is almost done, but he will do everything he can to retire as a Celtic.
Hopefully we get to see a few more KG/Pierce game because they are historic.