The Miami Heat’s Secret Weapon for a Title? Zone Defense.

One of the catchiest chants in the N.B.A. is an acknowledgment of one of the game’s most thankless tasks: “De-fense!” Clap. Clap. “De-fense!” It rained down this week as the Miami Heat coped with the nearly impossible challenge of slowing two of the league’s most fearsome players — the Denver Nuggets’ Nikola Jokic and Jamal Murray — during the N.B.A. finals in front of their home crowd.

The most exalted defensive matchups in the N.B.A. are typically one-on-one clashes, as opposing stars come face to face. But that is hard work. Really hard. Maybe you can stop an explosive scorer like Jokic or Murray for a possession or two. But every time down the floor? For 48 minutes? With an undersized roster that has endured the long grind of the postseason?

Good luck. For over 50 years, the N.B.A. refused to let teams do it any other way. It was man-to-man defense or bust. But now, teams can be more creative in how they go about trying to put the clamps on their opponents. And no team is more creative than the Heat, who play more zone defense — a scheme in which defenders guard areas of the court instead of individual players — than any other team in the league.

On Wednesday in Game 3, that meant having two players trap Denver’s inbounds pass, two more at midcourt and one protecting the basket at the far end — a 2-2-1 zone press — early in the second quarter.

By the time the Nuggets managed to get the ball upcourt, just 14 seconds remained on the shot clock, and the Heat’s defense had morphed into a halfcourt zone — a 2-3 set, with two players up top at the perimeter and three along the baseline. Murray, the Nuggets’ point guard, missed a 3-point attempt from the left corner, and the Heat raced away for a game-tying bucket.

Unfortunately for the Heat, that was about as good as it got for them in their 109-94 loss to the Nuggets, who took a 2-1 series lead ahead of Game 4 on Friday in Miami. Murray and Jokic both finished with triple-doubles for Denver, which, for one game, at least, was largely unfazed by Miami’s shape-shifting defense.

“We didn’t offer much resistance,” said Heat Coach Erik Spoelstra, who bemoaned his team’s lack of effort but considered it an anomaly. He added: “I think the thing that we’ve proven over and over and over is we can win and find different ways to win.”

And one of those ways is with their zone defense. There is a talent disparity in this series: The Nuggets have more of it thanks to their array of expert shooters and the all-around wizardry of Jokic, a two-time winner of the N.B.A.’s Most Valuable Player Award. So, in an effort to slow the pace of play and compensate for their lack of size, the Heat are occasionally abandoning their man-to-man defense by mixing in some zone.

This is nothing new for them. Miami played zone on a league-high 19.7 percent of its defensive possessions during the regular season, according to Synergy Sports, a scouting and analytics service. The Portland Trail Blazers, who played zone 14.9 percent of the time, ranked second, and the Toronto Raptors (8.4 percent) were third.

More important, the Heat — even amid the regular-season struggles that nearly kept them out of the playoffs — used their zone to great effect, limiting opponents to 0.937 points per possession. By comparison, opponents averaged 1.009 points per possession against their man-to-man defense.

Miami is playing slightly less zone defense in the playoffs — zone has accounted for 15.7 percent of its defensive possessions ahead of Game 4 — but no other team has come close to using it that often. And the Heat have had some success with it, holding opponents to 0.916 points per possession versus 1.003 points per possession with man-to-man defense.

“I think it’s effective,” Heat point guard Gabe Vincent said, “because it’s different.”

Jim Boeheim, who recently retired after 47 seasons as the men’s basketball coach at Syracuse University, was so renowned for his 2-3 zone defense that he became synonymous with it. But in his early years at Syracuse, he actually coached more man-to-man defense.

“We had a zone and we’d practice it, but not all the time,” Boeheim said. “But then we would be having trouble with somebody, and you’d put the zone out there, and they couldn’t score!”

Most teams did not practice it, and they seldom faced it in games.

“It can just screw somebody up,” Boeheim said. “And if your opponent is only going to one or two guys on offense, you can kind of cheat toward those one or two guys, and it can cause problems.”

The zone remains a bit of a novelty in the N.B.A., which essentially banned it for the first 50-plus years of the league’s existence. Before the advent of the shot clock in 1954, the worry was that too many teams would pack the area around the basket with defenders and slow the game to a crawl at a time when the league was desperately trying to grow its audience.

Later, critics considered the zone a gimmicky way for teams to camouflage poor individual defenders, especially as the league continued to glorify one-on-one matchups. The lowly zone was stigmatized. But over time, offenses stalled and scoring decreased as games devolved into a seemingly nonstop series of isolation sets, with players stationed on the weak side of the court to draw defenders away from the ball.

Ahead of the 2001-2 season, the N.B.A. had seen enough and eliminated its illegal-defense rule, which meant that teams could play zone — or use any other type of defense that suited them. The twist was that the change was designed to spur spacing and passing on offense.

The zone, though, remains fairly uncommon for several reasons. N.B.A. rosters are brimming with long-range shooters, and when passes zip from side to side, zone defenders are often too slow to react, leaving opposing players with open looks from 3-point range. Also, defenders are prohibited from camping out in the lane whenever they aren’t guarding an opposing player — otherwise known as the defensive three-second rule.

“And that changes everything,” said Alex Popp, the head boys’ basketball coach for IMG Academy’s postgraduate team in Bradenton, Fla. “N.B.A. coaches are still reluctant to play zone because you can’t just stick a guy in the charge circle and protect the paint.”

For the Heat, the zone has value. If it was initially born of necessity — as a way for Spoelstra to match up against bigger teams and hide some of his weaker defenders — it has become an asset. For long stretches of the Eastern Conference finals against the Celtics, Boston seemed flummoxed by Miami’s traps, and often settled for (errant) jump shots rather than attacking the rim.

Now, whenever the Nuggets bring the ball upcourt, they must do a mental calculation: What sort of defense are they about to see? The zone adds an element of unpredictability.

“I think it’s something that can work,” Boeheim said, “especially in short windows.”

Kyle Lowry, the Heat’s backup point guard, recently recalled a formative period of his childhood when his coaches taught him about the zone press, traps and the basic 2-3 formation. As he was asked about those experiences, he knew where the line of inquiry was headed.

“If you’re getting into the question of our zone, it’s pretty cool,” Lowry said.

OK, what makes it cool?

“It works sometimes,” he said.

Miami’s zone is not static. It changes from game to game and even from possession to possession, with dozens of permutations based on which opposing players are on the floor — or even Spoelstra’s whims.

Bam Adebayo, the team’s starting center, said they drill the zone “to the point where we’re tired of it.”

Spoelstra would rather walk on hot coals than discuss his schematic choices at the N.B.A. finals, but his players have acknowledged the zone’s amorphous nature.

“Spo does a great job preparing us all year to be ready for situations like this, to be able to switch in a timeout, switch a scheme, switch a defense,” Heat guard Max Strus said before Game 3.

For Game 4, Miami is likely to unveil a new scheme or a slightly different look. It may not matter — “I think Denver is too good,” Boeheim said — but the Heat have been in tough spots before. Their zone has helped.