by Marcel Mutoni@marcel_mutoni

With each passing day in these NBA Playoffs, it becomes clearer and clearer that the old guard is giving way to a younger, hungrier group of teams and stars.

The Boston Celtics are one of the last of the older squads, and the Miami Heat have an opportunity to end their era for good tonight.

Despite the Celtics’ struggles all series long — and the shortcomings of its biggest stars in key moments — the Heat know that tonight’s game represents an opportunity they can ill afford to let pass them by.

From the Sun-Sentinel:

“We have to finish it,” Heat coach Erik Spoelstra said Tuesday afternoon. “That’s what today was about: not relaxing, not exhaling.”

Smart move by Spo to call a rare practice the day after a road win. What better way to refocus the group and drive home the message that cannot be missed now. No time to strut. No time to rest. No time to look back with satisfaction at how this 3-1 lead in the best-of-seven Eastern Conference semifinals was built. No time to luxuriate in the Heat’s first win at Boston in four-plus years (and 12 games). No time for Chris Bosh’s primal overtime scream to echo for another few days.

“You don’t have time to feel good,” [Chris] Bosh said. “You sit back and think about it for a second. Then you snap back to reality and know that to eliminate them, that’s going to be the hardest game we’ve ever played.”

It’s unlikely that Boston will go down quietly; they’re a proud, veteran team with something left in the tank.

Tonight will help determine if the Celtics have enough left to withstand the Heat’s furious, desperate push, and further delay the inevitable future of the NBA.