Don't stop believing.
Boston defeated New York 97-90 in overtime, securing its first victory of the series to force a Game 5 in the Big Apple.
Led by Pierce's 29 points, eight rebounds and six assists, the Celtics managed to avoid an epic second-half collapse. They opened the third quarter with a 19-point lead that the Knicks trimmed to just three by the start of fourth quarter.
The Knicks managed to regain the lead during the final period, but the Celtics held strong and put themselves in a position to win the game in the final seconds. Pierce caromed a potential game-winning jumper off the rim, and after a failed in-bounds by the Knicks, Boston lived to fight another five minutes.
Jason Terry came up huge in the overtime period, knocking down a three to break the stalemate. Carmelo Anthony proceeded to answer with two of his 36 points, but Terry responded in kind, knocking down a two of his own. And the Celtics never looked back.
Their defense held the Knicks to just 34.4 percent shooting from the field (23.3 percent from deep), and their offense managed to eclipse 80 points for the first time this postseason.
Jeff Green pitched 26 points and six rebounds, and Terry's late-game heroics earned him 18 points.
Pierce and crew now head to New York down 3-1, where they will look to extend their postseason run further.
Not much can be made of a single victory while trailing 3-0 in a best-of-seven series, but this never-say-die attitude the Celtics assumed in Game 4 was electrifying.
Boston nearly blew a 20-point lead and is still faced with the reality of knowing that no team in NBA history has ever successfully come back from a 3-0 deficit, but the spirit of a winner, even if only for one game, was there.
It's no secret that the Celtics are in store for yet another franchise-defining summer. Pierce is under contract through next season and Garnett for two more years, but the feeling that this is the Celtics' last hoorah is gaining momentum.
Garnett finished the regular season banged up. He's spent most of this series in foul trouble and hasn't looked like the Garnett of old. He's just looked old. The prospect of retirement now looms over his head.
The fierce competitor in him scrapped and clawed his way to 13 points, 17 rebounds, six assists and one block in 37 minutes of Game 4, though. He played as if he had so much left to give, so much left to do. That intensity has never wavered—and neither has Pierce's.
These Celtics (specifically Garnett and Pierce) would never admit that their reign together is coming to an end. It's not their style. The significance of what is potentially their final playoff run isn't lost on them either.
Pierce knows the Celtics could part ways with him before next year. And everyone in Beantown is aware that the 36-year-old Garnett may contemplate, and ultimately submit to, retirement upon season's end.
This could be it. The end of an era. The next time the Celtics lose could be their last as they are. And if it is, they aren't going down without a fight, without a last stand.
'Melo and the Knicks are still in position to win the series. With J.R. Smith back in the fold, that win may (will?) come in Game 5 at Madison Square Garden. Boston's victory just prolonged the inevitable.
But it was also indicative of what these Garnett and Pierce-led Celtics are—resilient.
Pierce told his friends in New York that he would be there for Game 5 prior to Game 4. He wasn't done. These Celtics aren't done. Not yet.
This may have been Garnett and Pierce's last game together at home. Even if it wasn't, both are facing an offseason shrouded in ambivalence.
Will the Celtics trade Pierce? Will Garnett retire? Can this team (Rajon Rondo included) win as currently constructed?
There will be no shortage of questions to answer or issues to resolve for Boston this summer. The Celtics are old, fragile and aren't built to last. This victory, however, is.
When the Celtics lose, we can look to this victory and know they never stopped fighting. Whatever happens moving forward, we'll know they never put their fists down. They played horribly for three games, but didn't immediately fold when their backs were up against the wall.
They didn't stop believing. They never have. And regardless of what happens in the next game (or the one after that), so long as Pierce and Garnett are the two players that define the Celtics' emotional approach, they never will.
They'll go down the same way they initially came up—swinging.