The Miami Heat would be the first to assess their path to this late stage of the season as imperfect. Pretty much everything has posed a challenge. The injuries. The losses. Even their experience in the play-in bracket — a loss followed by a come-from-behind win — seems apocryphal, or at least true to form, now that they are facing the Denver Nuggets in the N.B.A. finals.

In the process, the Heat have co-opted adversity as a part of their identity. Adversity has hardened them and made them more resilient. Adversity has fueled their postseason run. Adversity has improved them as players and helped them bond as a team. Adversity has them competing for a championship.

Bam Adebayo, the team’s All-Star center, cited the “ups, downs, goods, bads” of the season as if they were inseparable qualities, as if none could exist without the others. Coach Erik Spoelstra has taken to occasionally describing his team as “gnarly” in the most complimentary way possible.

“That’s a Spo term,” Adebayo said at a news conference earlier this week, adding: “A lot of you in here probably never thought we would be in this position right now.”

The problem, of course, is that a steady diet of adversity takes a toll, and the Nuggets are a full meal. So much talent. So much size. So much depth. And not even the Heat, who have made a habit of navigating their way out of bleak situations, could match them on Friday night as the Nuggets pulled away for a 108-95 victory in Game 4 that has them on the cusp of their first N.B.A. title.

The Nuggets have a 3-1 series lead. Game 5 is Monday in Denver.

“It’s going to be a gnarly game in Denver that is built for the competitors that we have in our locker room,” Spoelstra said, adding: “We get an opportunity to play a super competitive game in a great environment.”

Spoelstra was notably upbeat, but that was nothing new. Count the Heat out at your peril.

“Our whole season hasn’t been easy,” Adebayo said. “It just seems like we won’t quit.”

They refused to quit after slipping into the playoffs as the No. 8 seed in the East. They refused to quit after losing two rotation players, Tyler Herro and Victor Oladipo, in their first-round series with the top-seeded Milwaukee Bucks. Herro broke his hand, and Oladipo tore a tendon in his knee.

The Heat wanted adversity? They flourished, eliminating the Bucks in five games.

They wanted more adversity? They nearly blew a 3-0 series lead to the Boston Celtics in the Eastern Conference finals before returning from the abyss to win Game 7 — in Boston — and advance. Afterward, Mike McDaniel, the coach of the N.F.L.’s Miami Dolphins, sent Spoelstra a text in which he described tough times as an opportunity, not that Spoelstra needed to be reminded.

“We share very similar thoughts about finding strength in adversity,” Spoelstra said.

Now, the Nuggets are loading the Heat up with more adversity than they can handle. Ahead of Game 4, Heat forward Kevin Love acknowledged that the team’s “room for error is so small.”

Duncan Robinson, Love’s teammate, pledged that their “urgency should be and will be at an all-time high.”

In the first quarter of Friday’s game, the Heat channeled that urgency by ditching their zone defense and matching up in man-to-man, which limited the Nuggets’ outside looks while cluttering up the two-man, pick-and-roll game that Nikola Jokic and Jamal Murray like to run.

Before long, the Nuggets established themselves. Sensing some space between himself and his defender, Jokic stepped back from 27 feet and made a 3-pointer. Nuggets forward Aaron Gordon sliced to the rim.

Early in the second half, Jokic dribbled straight at Adebayo, bumping up against him — once, twice, three times — before flipping the ball up and in with his left hand. A nifty bounce pass from Gordon to Murray led to a layup, a 10-point lead and a Spoelstra timeout. Some fans left in the fourth quarter.

“Some correctable things we’ve got to do,” said Jimmy Butler, who led Miami with 25 points. “But it’s not impossible. We’ve got to go out there and do it.”

The Nuggets got something that approximated a usual effort from Jokic, who collected 23 points, 12 rebounds and 4 assists while dealing with foul trouble. But he got ample help from the likes of Gordon, who scored 27 points, and Bruce Brown, who finished with 21 points off the bench.

Many of the Heat’s more unsung players have struggled in the series, and that hurt them again on Friday. Gabe Vincent finished with only 2 points, and Max Strus went scoreless. Miami wound up leaning on the veterans Kyle Lowry, who scored all 13 of his points in the first half, and Love, who made three 3-pointers.

Afterward, the Heat seemed cognizant of their new reality — that nearly everyone would be counting them out. Spoelstra called it “the narrative” that he said he was certain would circulate over the weekend. Butler, indicated that he did not care.

“We don’t have no quit,” he said. “We are going to continually fight, starting tomorrow, to get better, and then we are going into Monday to do what we said we were going to do this entire time and win. We have to. We have no other choice. Otherwise, we did all this for no reason.”

He added: “We’ve done some hard things all year long, and now it’s like the hardest of the hard.”

The challenge before them is great, though not insurmountable. The Cleveland Cavaliers came back from a 3-1 deficit in the 2016 N.B.A. finals, shocking the Golden State Warriors, who had set a record by winning 73 games during the regular season. Still, Cleveland is the only team to recover from that deep a hole in the finals; 35 other teams have tried and failed.

Spoelstra said he told his players in the locker room “to feel whatever you want to feel” after the loss. He did not expect them to get much sleep, and that was probably a good thing. He wanted them to stew on what had happened, and then refocus on the hardest-of-the-hard task ahead.

“Our guys love this kind of deal,” Spoelstra said.

The Heat wanted adversity? They definitely have some now.