They got within four entering the fourth quarter and then after eight ties in a riveting final stanza, they blew the older, tired Celtics away by scoring the last nine points over the final 1:38.
If Collins was beaming about his team's mental toughness before the game, you could only imagine his joy after this one.
"I don't know where to start," he said. "We just kept pushing and pushing. I just told the guys at halftime that we were going to keep fighting and keep grinding. That's all we do. It's not pretty, but now we have a chance for a Game 5 all even at 2-2 and we'll see where we go from there."
The whole basketball world wonders where this series goes from here.
At halftime, it not only looked like the Celtics were poised to run the 76ers out of their own building, but the way Magic Johnson and others were talking on ESPN, the guys in green seemed on their way to another world championship.
Hold the parade in Beantown, at least for now.
The Celtics are still a very talented team, perhaps even more talented than the 76ers. While the 76ers are still searching for a go-to guy, Boston has numerous options.
But they are older now, and when the 76ers got physical and toughened up in the second half, the Celtics backed off.
"We got caught up in the physical play and once we did, we never returned to playing basketball the way we did in the first half," said Celtics coach Doc Rivers. "In the first half, the execution was beautiful. In the second half, we just didn't do it. They took us out of a lot of stuff."
And now you wonder if the 76ers are capable of taking them out completely.