The NBA restart
The National Basketball Association's season went on hiatus on March 11. After Utah Jazz center Rudy Gobert tested positive for coronavirus, Commissioner Adam Silver immediately put a stop to the season. On June 4, the NBA's Board of Governors announced that that the league would finish up the regular season from July 30, after which teams would begin the playoffs.

All 22 teams flew to a sports complex at Disney World in Florida. On October 11 — exactly five months after the season was put on hold — the Los Angeles Lakers lifted the Larry O'Brien Championship Trophy for the 17th time in franchise history.
Upwards of 1,200 people, including players and personnel, were kept under strict watch for the three months it took to finish the season. The stringent restrictions paid off. Not a single person in the bubble tested positive for the virus.
Sugiura, Daisuke a veteran reporter and the only Japanese media member allowed inside the bubble, said he was "impressed by their rigorous management."

The US Open
On August 30, the United States Tennis Association (USTA) held the opening round of the US Open tennis championship in New York. While the tournament didn't include 1,200 people like the NBA playoffs, it was an international event that welcomed athletes from all over the world.

The players' accommodations were also different than the NBA. Whereas the basketball players and staff used hotels and resorts throughout Disney World, which allowed full isolation, the USTA used a single hotel — the Long Island Marriott — as the main accommodation. The players also had the option of making their own arrangements for the duration of the tournament.
Despite a less complete bubble than the NBA, the US Open succeeded in crowning its champion on September 12. During the entire two-week tournament, only one player and one staff member tested positive for the coronavirus.
Keys to a successful tournament
Both the NBA restart and US Open shared certain qualities that helped make their tournaments successful. Both utilized state-of-the-art technology to track the movements of players and staff.
As basketball players like Matisse Thybulle revealed on social media, NBA personnel in the bubble wore bracelets that they had to scan before entering every room. If a player was caught outside the facility without permission, he would be quarantined for 10 days, during which time he would be unable to play.
The NBA also put in place strict social distancing guidelines. Individuals were assigned to different "tiers": They received color-coded badges that separated them into groups, which dictated where they could and couldn't go. The badges also had a sensor that lit up or made a sound when people came too close to each other.

According to Long Island Marriott General Manager Mark Kulekci, tennis players and staff carried credentials equipped with tracking systems that were traceable by scanners set in doorways — much like the anti-theft detectors in retail stores. Security guards stationed every exit, which ensured that no one would be able to leave without the knowledge of USTA officials.
The Long Island Marriott went to great lengths to accommodate the players in other ways as well. Ballrooms were turned into a large weight-training area. The lobby became a makeshift marketplace selling food and drinks. The hotel restaurant served meals throughout the day — with staff behind acrylic screens for safety — along with the standard 24-hour room service.

The hotel's large parking lot allowed the USTA to not only set up a garden-style seating area with a large-screen TV showing the matches, but to operate "40 big buses to transfer about [700 to] 800 people every single day," Kulekci explained. It was one of the reasons the hotel was chosen as the main accommodation venue.
Of course, the biggest and most important aspect of virus containment is testing. The NBA had its players take a PCR test every other day; the USTA followed a similar schedule. Although the NBA's lack of positive tests made the point moot, constant and consistent testing would have been vital in identifying potential positive cases and initiating accurate contact tracing to keep infections to a minimum.

Olympic hurdles
Bubbles such as the ones run by the NBA and USTA have proven successful, but there are still questions when it comes to an event the size of the Olympics. One obvious issue would be the cost. The NBA bubble, while reportedly saving the league about $1.5 billion in losses it would have incurred from cancelling the playoffs, still cost $190 million to run. Scaling that up to an event the size of the Tokyo Olympics would require an absurd amount of money.

Another issue is whether athletes will buy in. Many of the superstars on the tennis circuit opted out of the US Open, whose bubble was even less isolated than the NBA's (although this should not be taken as a critique of the bubble per se).
No matter what other issues arise, there is no doubt that the NBA and the USTA achieved success with their approaches. These two examples can serve as a hint to how the organizers of the Tokyo Olympics might plan their tournament.

Kulekci gave a final piece of advice to Olympic organizers, saying that preparation, along with communication, is key. "The full information in detail needs to be obtained to make sure the expectations are clearly explained," he said. "It's teamwork. That would be the recommendation: to be prepared and planned."