MIAMI -- On a night LeBron James opened 1-for-6 from the field and Dwyane Wade scored just two first-half points, the Miami Heat found a way. Barely.

Even if it took a bit longer than planned.

Boston point guard Rajon Rondo was back to his dominant self, yet it still wasn't enough for the Celtics, as they fell to a 2-0 deficit in the best-of-seven Eastern Conference championship series with a 115-111 overtime loss at AmericanAirlines Arena.

"This group had resolve," Wade said.

In a game that offered some of the best both teams had to offer, the Heat ultimately prevailed behind 34 points from James and 23 from Wade, surviving an 44-point, 10-assist, eight-rebound effort from Rondo and 21 points from Celtics forward Paul Pierce, who fouled out in late in regulation.

The Heat overcame an early 15-point deficit, the largest comeback in the franchise's playoff history. The previous best were a pair of 14-point comebacks.

"We kept fighting, and Coach kept telling us to keep going," Heat guard Mario Chalmers said.

The ultimate warrior in this one, though, was Rondo, who played all 53 minutes.

"He was absolutely phenomenal," Celtics coach Doc Rivers said. "It's tough to have him play that way and not win the game."

The Heat appeared to put it away on a 3-pointer late in the fourth quarter from reserve forward Shane Battier, a pair of free throws from James and a jumper from forward Udonis Haslem.

But the Celtics stormed back to tie it 99-99 at the end of regulation on a 3-pointer from guard Ray Allen, who seemed to regain his stroke and his confidence.

"They don't leave me often, but they left me that time," said Allen, who shot 5-for-11 and scored 13 points.

Game 3 is Friday night in Boston.

"It just can't be any other way with this team," Heat coach Erik Spoelstra said of the Celtics, "and it has to be the hard way."

The Heat put it away in overtime when the Celtics basically ran out of gas.

"You don't throw it away," Rivers said of the loss. "You hold it for 24 hours, and then you move on. We've been very good about that."

With James hitting a pair of 3-pointers early in the third quarter, the Heat were able to close within five points.

But a third-quarter gamble also proved costly, with Spoelstra electing to open the second half with Joel Anthony at center in place of Ronny Turiaf. Anthony then was forced to the bench with his fourth foul with 9:34 remaining in the third period.

However, Haslem entered for Anthony, helping energize the Heat, amid the continued solid play of Chalmers.

In fact, when Haslem scored with 2:55 in the third, it put the Heat ahead for first time since 7-6 in the first quarter.

"We were able to stay into it mentally," Spoelstra said. "That's where I think we're different now."

And they were able to survive Rondo.

"It's kind of irrelevant. We lost," Rondo said of his statistical brilliance. "I felt fine. It was a mental grind for me individually and us as a team. There's no turning back, it's the conference finals."

The Celtics, with Rondo attacking and Allen again hitting shots, pushed to a 15-point lead early in the second period and went into halftime up 53-46.

It was a first half of considerable concern for the Heat, with Wade scoreless on 0-for-5 shooting before converting a layup with 27 seconds to play in the second quarter, raising concerns of a repeat of his struggles early in the previous round against the Pacers, before he took treatment on his left knee.