MIAMI -- Less than a second away from their second trip to the NBA Finals in four seasons, Miami Heat players and fans stood in collective shock after Boston Celtics guard Derrick White tipped in the go-ahead bucket at the buzzer in a stunning 104-103 loss Saturday night in Game 6 of the Eastern Conference finals.

The shot forced Game 7 on Monday and pushed the Celtics to within one victory of becoming the first NBA team to come back from a 3-0 deficit to win a playoff series.

Despite the emotions of the loss, Heat coach Erik Spoelstra and star forward Jimmy Butler were defiant in the belief that they could still find a way to win the biggest game of the season on Monday night.

Spoelstra called the final sequence a "shame" but said he has "no regrets."

"This is the way this season has been," he said. "This is one hell of a series. At this time right now, I don't know how we are going to get this done, but we are going up there and get it done. And that's what the next 48 hours is about."

Butler, who hit three clutch free throws with three seconds left to give the Heat a 103-102 lead, said he remains confident the Heat will find a way to win Game 7, despite the fact that they've now dropped three straight, including being on the wrong end of one of the wildest finishes on Saturday night.

"[That's] basketball for you, basketball at its finest -- very, very, very entertaining," Butler said. "But that's good basketball. I think, I believe, as we all do, like you're going to get the same test until you pass it, I swear. We were in this same position last year. We can do it. I know that we will do it. We've got to go on the road and win in a very, very, very tough environment."

It's the same tone Butler tried to set heading into Games 5 and 6, exuding belief that the Heat would find a way to close out the series. He acknowledged frustration, though, over his 5-for-21 shooting night, saying the Heat wouldn't have been in position to lose on a buzzer-beater if he had been "better from jump street."

"Everything that happened tonight, if I don't go 5-for-21 and turn the ball over and all of this good stuff, it's a different story," he said. "I've got on a different hat up here and we're getting ready to go to the Finals."

The Heat's postgame locker room Saturday night was the quietest it has been in recent memory until guard Gabe Vincent turned on a song from his phone -- "Life Goes On" by Ed Sheeran. The Heat are trying to hold the same mantra as they face a Celtics team that has found its confidence again over the past week and appears even stronger now, given how the final seconds played out in Game 6.

"It's almost storybook," Vincent said. "It's almost like it's supposed to be this way. But you know, go to Boston and get a win."

The Heat are buoyed by the fact that they've played in several close games all season and have withstood every challenge that brought them to this point. Heat center Bam Adebayo, who struggled through a 4 for 16 shooting performance on Saturday, was quick with a response when asked how the Heat can emotionally recover from the loss.

"You go in to Boston and you get you one," he said.

The Heat also are trying to generate hope from the idea that they've always played better when they've made things more difficult on themselves throughout the campaign. Trying to get over this type of letdown, however, would be one of the biggest accomplishments of Spoelstra's Hall of Fame-worthy career.

He set the tenor for his group while sitting behind the postgame podium late Saturday night.

"There's been nothing easy about this season for our group," Spoelstra said. "And so we just have to do it the hard way. That's just the way it's got to be for our group.

"We wish we would tip this thing off right now. Right now, let's tip this thing off, and let's play another 48 minutes. But we'll wait 48 hours and do this thing in Boston."