In the NBA, deception is standard protocol. Players change speeds, switching from fast to slow and then back to their quickest gear. They use their eyes to set up no-look passes. They go behind the back with a dribble into spins and fakes to throw defenders off balance. They flop to fool referees. They initiate a running motion through a screen before pivoting back the other way. It’s all a means of feigning disorder, a military strategy millennia old.

The game is always evolving, and there will always be new ways to use the game’s conventional wisdom against an opponent. But if the root of deception is doing something that someone would not expect of you, then why hasn’t the NBA embraced zone defense?

Back in November, the Rockets were throttling the Nets by 21 points in the first quarter. It was a performance not unlike most other nights for Houston, which has posted one of the greatest offensive seasons in history. It looked like another loss for Brooklyn. It was. They lost 117-103. But something interesting happened toward the end of the first quarter. Brooklyn switched from its standard man-to-man defense to a 3-2 zone, an unusual move against a team as shot-happy as the Rockets.

Teams don’t use zone mostly because most modern offenses are built around shooting and ball movement, which can stop the scheme dead in its tracks. A zone defense requires players to defend an area of the court and guard the opponent only when the opponent is in his designated area. When the ball is swung from one side of the floor to the other, the perimeter defenders inch toward the side with the ball. Meanwhile, wings and bigs form the back line of the zone and protect the paint and corners. Moving the ball from one side of the floor to the other, with dribble penetration and several crisp passes, can shake a zone like a snow globe and easily open up a shooter. It’s easier for offenses to tear holes in zones, where gaps are inherent to the scheme, than with cohesive man-to-man defense.

You’d think a team like the Rockets, which takes and makes more 3s than any team in history, would be the last team you’d want to use a zone against. But the Nets did it anyway—they had to do something to give themselves a chance. “I’ve always thought about it, never had the guts [to] as a new coach: Man, I’d love to play a zone. No one does. Why can’t I? I know Don Nelson did it, Rick Carlisle does it, those guys who have some credibility in this league,” Nets coach Kenny Atkinson told reporters. “We threw it out at a timeout. We got a stop. If they would’ve scored we probably never would’ve played it again. We got a stop and we kept playing it.”

The zone improbably stymied the Rockets offense, and changed their play calling. Houston ran fewer pick-and-rolls, which meant James Harden wasn’t being put into isolations, which have devastated opponents this season—the Beard is having one of the greatest iso-scoring and iso-playmaking seasons ever. Harden wasn’t shimmying into the lane with Clint Capela rumbling by his side; the lob dunks disappeared, and so did the kickout passes for 3s. Instead, the Rockets passed the ball more often around the perimeter, searching for 3s. Against the Nets, they logged 2.8 passes per possession, an uptick from the 2.3 passes per possession they’ve made over the rest of the season, according to data calculated using a combination of stats from NBA.com and Synergy. They simply didn’t look the same.

This isn’t what Rockets basketball looks like. They ended up getting a solid look with an Eric Gordon spot-up 3, but the process of finding that shot took them out of their comfort zone. Houston plays at a slow, deliberate pace, runs pick-and-roll on nearly every possession, and passes the ball less than all but one team in the NBA (Oklahoma City). But they dribbled less and passed more against Brooklyn. The freaking Nets made the freaking Rockets totally change their hallmark style simply by running a zone. “Maybe in a game like this, you discover something,” Atkinson told reporters. “Maybe it’s a strategy we can use going forward.”

The Nets cut the lead to four, but it wasn’t long after that Houston began picking the zone apart by feeding Capela and letting him make plays when the defense collapsed or by sending cutters into the lane. The Rockets also ran their pick-and-roll anyway. After the NBA eliminated the illegal defense rule in 2001, modern man-to-man defense took zone concepts by having weakside defenders helping off the ball, which makes it more like a hybrid. It’s not as if the defensive principles against a pick-and-roll aren’t similar. But the fact the Nets—a team that lacks elite defensive personnel and had seldom practiced the zone until it desperately pulled the strategy out late in the first quarter—could force the most lethal offense in the NBA to change its style of play, even for a spell, spoke volumes.

The Rockets might be better prepared for a zone defense in the playoffs. The lengthy playoff schedule gives coaching staffs time to make necessary game-to-game adjustments. And with that time, the Rockets could design plays that can pick apart a zone. They certainly have the personnel to do so. One NBA assistant coach noted that it’s not a coincidence that the zone’s prominence deteriorates as the level of competition increases. It’s a mainstay at youth and high school levels, drops off precipitously in the NCAA, then falls almost entirely off the map in the NBA. The greater the talent level, the harder it is to play zone. Players in the Association have so much speed, athleticism, and skill being enhanced in systems that emphasize shooting and spacing; utilizing a zone against the best players in the world presents a monumental risk.

But for teams with the odds stacked against them, a zone is worth trying: The strategy was one of the biggest features of Dallas’s shocking championship run in 2011 that went through the Blazers, Lakers, Thunder, and LeBron James’s Heat.

No team has used zone over this decade more frequently than the Mavs. One of the chief architects of their 2-3 zone was Dwane Casey, who was a Dallas assistant from 2008 through 2011 before being hired by Toronto. Casey would clench his fist to signal to players to run zone, usually after made baskets, though sometimes after misses. It didn’t give opponents time to mentally or physically adjust, and if even they did, the Mavs might be back in man-to-man the following possession. It’s like a baseball pitcher using breaking balls like curveballs and sliders to keep the hitter off-balance rather than throwing fastball after fastball.

The Heat were heavy favorites to beat the Mavericks before that Finals; the way in which the zone discombobulated the Miami offense is one of the reasons Dallas came out with the upset. The Mavs used deception to turn the series on its head against the Heat. And zone has been utilized in other series. The Suns and Spurs implemented it in playoff series in the early 2010s, and the Celtics used it in recent years as a means of hiding Isaiah Thomas. But over the past few years, zone usage has dipped drastically. Though 28 teams have run zone for at least one play this season, only six have done it for over 25 possessions and only the Mavericks have for over 100 (and that accounts for only 3.2 percent of their plays). By comparison, an average of 18 teams between the 2009-10 and 2012-13 seasons used zone over 100 times over the full season, compared to an average of four over the past five seasons.

It’s not completely gone. Since March 23, the Spurs and the Celtics, led by two of the league’s best head coaches, mixed in 2-3 zone defense for an extended stretch over a total of five separate games. The Spurs first turned to the zone while down 12 to the Bucks to open the second quarter before stopping in the third, and then they used zone when trailing by 22 entering fourth quarter against the Wizards. Boston went to a zone in the second half to close a game against the Jazz, and then again late in the fourth quarter against the Raptors. The Celtics also showed the Bucks another zone on Tuesday night, sprinkling it in at the end of the first and fourth quarters, and the beginning of the second.

For what it’s worth (and it isn’t worth much), the Spurs lost both games they went to the zone; the Celtics went 2-1, with their loss to the Bucks coming in a game where two-way player Kadeem Allen was the starting point guard. The little zone wrinkles Gregg Popovich and Brad Stevens introduced feel like small research and development sessions in preparation for the playoffs. Pop’s zone helped lure the Bucks into a tough midrange jumper from Thon Maker—not an ideal shot for the Bucks:

During all five instances, the opponent was stalled out, at least for some time. With Pop having already conceded the game against the Wizards, he implemented a zone for the entirety of the fourth quarter, largely against Washington’s second unit—the Spurs were able to force turnovers and create some transition chances in the process. After substituting personnel that could space the floor, the Bucks used their size and athleticism to attack the paint, then kick out passes for 3s against San Antonio defenders. The result was similar for the Celtics on Tuesday, as Milwaukee was able to get to the lane and find open shooters.

Utah was initially puzzled by the zone, like the Jazz are in the clip above. They eventually made adjustments by making more decisive passes and improving their ball movement, but Boston went back to the zone late in the game, and held them to just two points over the final 2:25. It was as if the Jazz forgot what had worked during the first stint.

Perhaps the most interesting usage of the zone came from Boston in its game against the Raptors. While leading 97-94 with five minutes to go in the fourth, they went zone for five consecutive possessions and increased their lead before switching back to man-to-man. Over that short stretch, the Raptors turned the ball over three times and hit only one shot (a miracle corner 3 off a screen by Kyle Lowry). Toronto’s offense was effectively neutralized.

Faced with the zone, the Raptors could barely get the ball into the paint; under normal circumstances, they generally get to the rim at will, scoring 43.3 percent of their points in the paint this season, which ranks 11th in the NBA. Much like the Rockets, the Raptors were forced to play differently. Boston quickly went away from the zone and closed out the game with its regular scheme, but that short run was all it needed to secure its late-game lead. There wasn’t any time left for Casey or the Raptors to make adjustments.

From conversations with people ranging from NBA executives to coaches to video coordinators, the common trend is that head coaches are hesitant to run zone because they don’t practice it. Zone defense requires a set of rules that are hard to commit to on every possession, so there’s less room for error. A lack of communication and one missed rotation can result in a wide-open layup. Players don’t have the same discipline as they do playing man-to-man, and even if it is drilled, the benefits may not be as significant as time dedicated to practicing plays or situational preparation.

Zone will never become a primary defense for NBA teams due the nature of the league, but it can be used to change the flow of a possession, and thus, break the rhythm of a team. Every play matters in the postseason, and even a handful of successful zone possessions over a mere two minutes could be the difference between a win or a loss. For the teams that need to increase their risk profile to have a shot against the favorites, it at least seems like a plausible strategy to employ.