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How The NBA Is Using Summer League — And Virtual Reality — To Train Refs

Partway through a postgame video review within the bowels of the arena, referees Cheryl Flores and Robert Hussey hang their heads in dismay and disbelief over a missed call.

Today’s crew is overseen by 10th-year veteran NBA referee Ben Taylor, who has just pointed out the officiating error on a monitor in the locker room. Both of his charges are distraught upon realizing their mistake. Was this the NBA Finals? Was it an egregious missed call, the sort that may have swung the outcome of a close game?

Not quite. The call in question took place at the NBA’s summer league in Las Vegas, and the rule at issue is so obscure, the average NBA fan likely isn’t aware of it: When the crew stopped play for a bleeding player1 in the first half, they left the shot clock at its previous position of 12 seconds; it should have been reset to 14 by rule.

So why are Flores and Hussey so upset over a seemingly minute blunder in an inconsequential summer contest?

Pride is at play, certainly. There’s more to it, though.

Both officials are near the end of the NBA’s developmental pipeline, where competition is fierce for coveted full-time roles in the world’s biggest league. As the NBA looks to round out its staff ahead of the 2022-23 season, each is among the prime candidates to fill open slots. Only about 70 such jobs are available at any one time; Flores and Hussey have risen to the top of a program that once included thousands of people. Even in summer league, every call makes a difference, with high-ranking league staffers parsing officials’ every move.

This is just one window into the NBA’s officiating program in Las Vegas, which has come to serve as a central hub for referee training and development in recent years. For prospective officials, summer league is a chance to learn on the court and in detailed review sessions. For the league, it’s a chance to grade the next generation of refs who will someday be making these kinds of calls in the NBA Finals. The setup for this process has become more advanced and detailed with each passing summer — this year, it even features new virtual reality technology poised to revolutionize the entire world of officiating. And all of this is happening around games that NBA fans might not even be following. 

Taylor serves the role of trainer for summer league refs — part of a long-running mentorship program the league organizes each year.2 He fondly remembers his own time as a young ref at summer league, where he once called Kevin Durant’s first-ever NBA action in Vegas in 2007. Taylor says the hands-on training he received from officiating legends like Joey Crawford and Derrick Stafford served as the foundation for a successful career, and he uses it as a model for the tutelage he offers younger officials today.

But he also remembers how different the setup was back then.

“I got hired into the D-League at 21 [years old],” Taylor told me. “Ben Taylor today, at 21, would barely be in the introductory levels of this [program].”

The league’s approach to summer programs has evolved immensely in a short time. When Taylor was learning, summer league invites were typically extended as a tryout of sorts; evaluators often had never seen the refs they invited, outside of a handful of games at a camp they happened to be attending. The refs who impressed NBA staffers during summer play would regularly get hired directly into what was known then as the D-League, immediately placing them on a track toward a full-time NBA gig.

Today’s officiating program is far more layered and detailed. Securing an invite to summer league means rising through multiple tiers of the league’s developmental hierarchy. For instance, only once an official is on the G League’s staff can that official even be considered for a summer invite, and a G League spot is itself exclusive. (Last year, the league hired only 13 new G League officials.)

Only 13 of over 3,000 refs make it to the cusp of the NBA

Stages of the 2022 NBA referee recruiting process, where only a portion of candidates from each level advance to the next

Level Referees
Recruitment NBA scouts canvass the globe for program candidates. ~3,000
Grassroots camps Those truly interested attend one of several basic camps. 96
Mid-level camp The best Grassroots refs proceed to mid-level programs. 48
ELITE camp Top graduates from mid-level camps move to ELITE program. 25
G League* A few refs are hired from ELITE into the G League each year. 13

*Number listed is new G League hires from the ELITE camp. There were 60 total G League referees in 2021-22.

Sources: NBA,

This formal selection process means the summer league is serious business for aspiring refs. 

“It’s a huge honor,” Flores said. “In our mind, these games are as [important as] an NBA game, because that’s what we strive to get towards.”

And working games is just one part of the program for the officials who make it to Vegas. They also attend daily morning meetings run by Monty McCutchen, Mark Wunderlich and other members of the NBA’s officiating department.

Imagine a college lecture setting, but for refs: They review plays and concepts, discuss rule changes and more. At one such meeting this summer, McCutchen spent the better part of an hour breaking down the new transition take foul rule implemented by the NBA’s board of governors — what will qualify, what won’t and how the league anticipates players trying to exploit the new rules.

In other words, it’s a chance to be fully immersed in the craft of calling games.

The stakes are particularly high for Flores, Hussey and a handful of others at the top of the pipeline, as they are being considered for promotion to full-time NBA roles.

Both are part of the NBA’s group of “non-staff” officials — a small collection of refs who, in recent years, have alternated between the NBA and the G League (and the WNBA, in some cases). They’ve worked select regular-season NBA games; the collective-bargaining agreement allows 50 total assignments for all non-staff officials each season, as a way of allowing up-and-coming refs to test their chops at NBA game speed.3 Non-staff officials have also continued their work in the G League during this time, primarily as crew chiefs.

When openings come available on the full-time NBA staff each offseason, these non-staff officials are the first ones considered. Maybe just one will be hired; maybe three or four will get the nod; some years, none will make the cut.

“It’s about the talent sets of people who are ready or not ready,” McCutchen said of this process. “You may have a need for four spots, but only have two [referees] that are really ready. So that combination and balance of [who] is ready and what is needed always informs that decision every year.”

Many variables factor into who gets the call, including referees’ analytical profiles derived from the league’s tracking and grading programs. In a way, though, summer league — and preseason play a few months later — is a final audition for refs like Flores and Hussey.

“How we referee here is how we would referee in an NBA game,” Flores said. “Summer league, for us, is like our NBA.”

While officials and their trainers focus on the details of the job at the Thomas & Mack Center, others within the NBA are busy with another project elsewhere on the University of Nevada, Las Vegas campus, one that’s drawing excited whispers throughout the league’s officiating department: an immersive form of referee training based on virtual reality technology.

They’re working with Rezzil, a U.K.-based company focused on using tech to aid in cognitive development in sports.4 As part of the league’s new Launchpad technology program, Rezzil spent much of the past year working with the NBA to develop a virtual reality platform that’s poised to flip the world of referee training on its head.

Using a system that draws data from optical-tracking companies like Second Spectrum and Hawk-Eye, Rezzil creates a three-dimensional, virtual reality rendering of any part of an NBA game.

“It looks like a video game,” Andy Etches, a co-founder of Rezzil, told me. “But it’s actually the game. Every single player will be in the right position, their body parts will be accurate, the shape will be accurate.”

With nothing but a VR headset and a laptop, users of this system are immersed directly onto the virtual “court.” They can view play from any perspective — their own, sure, but also that of any other ref or player on the court (or from fixed areas such as the scoreboard or baseline).

“They have some really interesting smoothing algorithms that just make it look, basically, like NBA 2K,” said Tom Ryan, NBA vice president of basketball strategy and guru of all things tech. “It looks and feels really close to real life.”

Users have a full host of features like pause, rewind and slow motion. And the system has the ability not only to re-create any play or sequence from a past game but also to generate new, hypothetical settings.

The NBA chose Rezzil for this project after close collaboration with many in referee operations. The possible implications on the world of referee training are almost inconceivably vast.

Currently, NBA refs train primarily through the REPS program, a back-end system that categorizes all their games and provides numerous camera angles from which they (and their trainers) can evaluate and improve their performance. But before long, with Rezzil’s help, REPS could look very different.

“REPS has nine camera angles [for a given play],” McCutchen said. “We think, eventually, this is going to be our 10th angle.

“Not only will it show you a camera angle, we’ll be able to virtually move the referee. If I’m telling them, ‘You would have seen this play better had you taken a step down,’ they’re going to be able to click on [that play in Rezzil], move themselves one step down, and see … how that play would open up for them had they made this mechanical adjustment.”

Details are still being worked out on the business side; no full-on agreement between the NBA and Rezzil yet exists. But the league has already verified many of Rezzil’s basic concepts, and sources on both sides of the table feel there’s real momentum toward a partnership.

Before long, some envision this immersive technology not just as part of the referee training program, but as its entire foundation, much like simulators are used in other fields.

“It’s not novel in other industries,” Ryan said. “If you’re an astronaut, you do flight simulations. … It’s very common to get those cognitive reps in.”

So within just a year or two, up-and-comers like Flores and Hussey could be in that same locker room inside the Thomas & Mack Center — only instead of watching plays on a monitor, they’ll put on a VR headset and jump right back onto the floor, this time virtually.

Training for referees isn’t as simple as for players, who need only a ball and a hoop to practice shooting; to truly work on their craft, NBA refs need 10 high-level players on a court together. And traditionally, it hasn’t always been easy to create more opportunities for prospective officials to get that kind of real-time experience.

But that’s changing. Whether it’s calling in-game action within the league’s developmental path or the promise of virtual reality, aspiring refs have more chances to learn the craft and show they belong at the game’s highest level. In turn, that has created real excitement about the future of referee development.

And summer league is at the center of it all. Through the combination of an improved talent pipeline, cutting-edge tech and various other available tools, the summer has become an important time for testing and training the referees of tomorrow’s NBA. So expect plenty more agonizing over shades of meaning in the rulebook and how it applies to seemingly trivial summer league outcomes — the league wouldn’t have it any other way.

CLARIFICATION (July 21, 2022, 3:32 p.m.): A previous version of this story suggested that Hawk-Eye is an NBA partner. While the league does use Hawk-Eye data internally, the company is not an official partner.


  1. Known as “infection control” in the fancy terminology refs use.

  2. Other full-time NBA refs, such as John Goble and Josh Tiven, share Taylor’s duties this year.

  3. This number was expanded due to COVID-19-related needs over the last two seasons, per McCutchen, but should return to the usual 50 moving forward.

  4. Rezzil is active in several professional soccer leagues, including major European leagues and MLS.

Ben Dowsett is a writer and videographer based in Salt Lake City. His past NBA work can be found at ESPN, GQ, The Athletic and elsewhere.


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