BOSTON -- As they find themselves on the precipice of the 2022 NBA Finals, the Boston Celtics might find motivation in a series that happened a decade ago.

The Oklahoma City Thunder were near the top of the basketball world in 2012, having reached the Finals with a roster featuring three future MVPs -- Kevin Durant, Russell Westbrook and James Harden -- all of whom were within their first five years in the league.

When the Thunder lost to the Miami Heat in five games in the Finals, the assumption was it would be the first of many OKC appearances in the NBA's championship round. They appeared to be a dynasty in the making.

That dynasty never happened.

Harden was traded to the Houston Rockets before the next season began, and year after year, a combination of injuries, bad luck and excruciating playoff losses saw the Thunder fail to return to the Finals before eventually breaking apart.

The lesson? Don't assume another chance is coming.

That Thunder team is one example of how fleeting the kind of moment the Celtics have in front of them can be. They host the Heat in Game 6 of the Eastern Conference finals (8:30 p.m. ET, ESPN) with a chance to close out the series and return to the Finals for the first time in 12 years.

"This is a great opportunity," Boston's Jaylen Brown said after the Game 5 victory. "Leave everything on the floor. You don't want any feelings of regret."

The Celtics have made it to the East finals six times since that last Finals trip in 2010. This, however, is arguably the closest they have been since they found themselves in the same position a decade ago: heading home to TD Garden after winning Game 5 of the East finals against the Heat to take a 3-2 series lead.

The difference was those Celtics -- an aging team led by Paul Pierce, Kevin Garnett and Ray Allen, with one title and another Finals trip under its belt -- were going up against LeBron James at his peak. James went on to play the game of his life to deliver Miami a win before the Heat would secure Game 7 and, eventually, beat the Thunder in five games as James won his first championship.

Six years later, the Celtics were in a similar position, leading James -- in his second stint with the Cleveland Cavaliers -- 3-2 in the series. James dropped 46 points, 11 rebounds and 9 assists to tie the series in Game 6, and while then-rookie Jayson Tatum threw down a memorable dunk over James in the fourth quarter in Game 7 in Boston, it was James and Cleveland who prevailed.

"Yeah, it does," Tatum said with a smile when asked if it feels different to be in this position now than it did four years ago. "I'm a lot better, [Brown] is. We're just older. And we've been through those tough times."

In 2020, the Celtics ran up against the Heat in the bubble, falling in six games.

This year, the Celtics are the clear favorites. While Boston has dealt with its share of injuries -- Robert Williams III's recurring knee issues, Marcus Smart's right leg injuries and Al Horford missing Game 1 of the series due to NBA COVID-19 health and safety protocols -- Miami has been decimated by them.

The Heat's three best perimeter players -- Jimmy Butler, Kyle Lowry and Tyler Herro -- are either playing with obvious limitations or unable to participate at all. Even if all of them were healthy, the Celtics' league-leading defense is putting an already suspect Heat half-court offense into a sleeper hold.

"If you want to break through and punch a ticket to the Finals, you're going to have to do some ridiculously tough stuff," Heat coach Erik Spoelstra said after Game 5. "Getting on to Boston and figuring that out collectively, those are the emotions and the breakthroughs that you have that you remember the rest of your life."

Four months ago, none of this seemed possible. Boston was floundering around .500, seemingly meandering its way to a second straight mediocre season. But thanks to the combination of timely transactions, improved health and coach Ime Udoka's philosophies translating into success on the court, Boston turned into a juggernaut that was the NBA's best team for the final two-and-a-half months of the regular season.

Now the Celtics find themselves with their best opportunity, after years of knocking on the door, to finally break through.

"Nothing changes," Udoka said of the team's mindset heading into Game 6. "We had to come out with the right mentality after a win, and we did that. We want to do the same [in Game 6], close it out at home."

This is only Tatum's fifth NBA season, but his third East finals. It's the fourth for Brown in six seasons, and the fourth for Smart in eight. It's both a reminder of how much playoff experience Boston's young core has together, and how hard it is to make it to that final step.

The Celtics hope their experiences will be enough to prepare them for the biggest game of their lives Friday, when they'll have a chance to punch their ticket back to the Finals.

Like that Thunder team, the Celtics look like a group that could be positioned for an extended run of excellence. Seven of Boston's top eight rotation players are between the ages of 23 and 28 (Horford, 35, is the lone exception). Five of them are 25 and under.

If Boston does reach the Finals, Tatum and Brown will become the fourth 25-and-under tandem to do so while leading their team in scoring in the past 40 years, according to the Elias Sports Bureau.

The other three? Hakeem Olajuwon and Ralph Sampson with the Houston Rockets in 1986, Shaquille O'Neal and Anfernee Hardaway with the Orlando Magic in 1995 and Durant and Westbrook in 2012.

None of those tandems made it back a second time.

"We got an opportunity to do something with this group that's special," Brown said. "So let's not take that for granted. Let's come out Friday on our home floor, and play the best version of basketball we played all season."