NATIONAL Basketball Association (NBA) commissioner Adam Silver on Tuesday voiced concern that a “significant spread” of the coronavirus could potentially expose a “hole in our bubble” and shut down the season a second time.

Silver made the comments during Fortune’s virtual “Brainstorm Health” conference.

The NBA commissioner expects that players will test positive for the coronavirus but said he’s “not sure yet” what the league’s threshold will be for having to shut down the season at ESPN’s Wide World of Sports campus at Disney World near Orlando.

“Certainly, if we had any sort of a significant spread at all within our campus, we would be shut down again,” Silver said. “It would be concerning if once [the players] sit through our quarantine period, and then were to test positive, we would know that, in essence, there’s a hole in our bubble.

“That our campus is not working in some way.”

The season is set to restart July 30 with a 22-team tournament, with scrimmages slated to begin July 22. Silver postponed the season March 11 after Rudy Gobert of the Utah Jazz was the first NBA player to test positive for COVID-19.

Strict protocols — including quarantines and COVID-19 testing for players and personnel — will be in place, including contact tracing.

“We can analyze the virus itself and try to track whether, if there’s more than one case, if it’s in essence the same virus, the same genetic variation of the virus that has passed from one player to another,” Silver said.

Silver said he’s confident enough in the league’s protocols that he plans to attend after being tested himself, but added he will “stay far away from players.”

“This should work,” he said. “But again, this virus has humbled many, so I am not going to express any higher level of confidence than we are following the protocols and we hope it works as we designed it.”

Meanwhile, a fourth Brooklyn Nets player, forward Taurean Prince, has tested positive for COVID-19 and will sit out the NBA’s restart later this month, ESPN reported Tuesday.

The Nets were already without center DeAndre Jordan, guard Spencer Dinwiddie and forward Wilson Chandler, who opted out after positive tests. Forward Kevin Durant (torn Achilles) and guard Kyrie Irving (shoulder) were never expected to play as they continue to recovery from surgeries.

According to ESPN, the Nets left for Florida on Tuesday evening.

The Nets, who sit seventh in the Eastern Conference at 30-34, can add four players to the roster to replace the four who have tested positive. Training camps are expected to open next week, with games beginning July 30.

Brooklyn’s first game is against the Orlando Magic, currently a half-game back in eighth in the East, on July 31. The Nets will play seven more games while trying to avoid a play-in for a playoff spot.

Prince, 26, averaged 12.1 points and six rebounds in 64 games (61 starts) before the regular season was paused in March. In his fourth NBA season and his first with Brooklyn, he has career averages of 11.6 points and 4.3 rebounds. — Reuters