As the first N.B.A. teams arrived at Walt Disney World for the resumption of their season, Commissioner Adam Silver reiterated his conviction that the restricted environment in Florida will be safer for the league’s personnel during the coronavirus pandemic than being anywhere “off this campus.”

The ultimate test of that belief had begun just a few hours before Silver’s comments, when the Orlando Magic — courtesy of a 30-minute bus ride from their home arena — were the first of the 22 teams to arrive Tuesday morning at Walt Disney World to begin life in the N.B.A.’s restricted-access village.

Denver, Phoenix, Utah, Washington and the Nets were also scheduled to arrive Tuesday, with eight teams to follow on Wednesday and eight more on Thursday. After weeks of planning and the creation of a 113-page guidebook of health and safety regulations to govern the N.B.A.’s return to play on July 30 after a more than four-month hiatus, Tuesday’s check-ins were the beginning of a critical process: assimilating teams into the campus while trying to keep the coronavirus out.

“It’s a very protected environment, but, again, this virus has humbled many,” Silver said on Tuesday on Fortune’s Brainstorm Health virtual panel. “So I’m not going to express any higher level of confidence than: We are following the protocols and we hope it works as we designed it.”

Jeff Weltman, Orlando’s president of basketball operations, spoke with reporters via Zoom as members of the Magic’s traveling party settled into their quarantine at the Grand Floridian, regarded as the second-tier choice of the three Disney hotel properties to which teams were assigned based on playoff seeding.

“This has never been done before,” Weltman said. “All you can do is prepare yourself as best as possible given the very restricted modes of operation that have been placed upon us. Our guys have done that and now it’s time to come together.”

Those who arrived Tuesday were almost immediately taken to a testing room. While on campus, they will be tested for the coronavirus daily, and masks will be mandatory in public when teams are away from basketball activities. After arrival, players and staff must quarantine for up to two days and register two negative tests before they can move freely around the premises.

A significant fear is that players or staff members who initially register negative tests are actually carrying the coronavirus, which medical experts say can incubate for up to two weeks. To help mitigate that threat, players also received two optional devices in their rooms: A beeping sensor to remind campus residents to maintain at least six feet of distance between themselves whenever possible, and an Oura ring, which may help provide early warnings of Covid-19 symptoms.

“I have been very optimistic for quite a while now, only because I know the lengths to which and the extent that the N.B.A. has relied upon experts and tried to leave no stone unturned,” Weltman said.

Yet even as the first teams arrived, two more high-profile players were ruled out for the rest of the season on Tuesday: Washington’s Bradley Beal and the Nets’ Spencer Dinwiddie.

Beal’s decision was not a surprise, as he had voiced numerous concerns about safety and the restrictions on players once inside the N.B.A. bubble. He was officially ruled out because of the lingering effects of a shoulder injury, leaving Washington without its three best players: Beal, the injured former All-Star John Wall and Davis Bertans, Washington’s sharpshooting forward who recently announced that he would not play to guard against injury as he enters a potentially lucrative off-season as a free agent.

Dinwiddie, who tested positive for the coronavirus last week and again Monday, has experienced headaches and dizziness. He announced on Twitter that he and the Nets made a joint decision to end his breakout season while he remains symptomatic. Averaging 20.6 points and 6.8 assists per game, Dinwiddie is one of at least five Nets veterans who will be unavailable for the restart, joining Kevin Durant, Kyrie Irving, DeAndre Jordan and Wilson Chandler.

The Nets were in talks Tuesday to sign the veteran center Amir Johnson to replace Jordan, according to two people who were not authorized to discuss the team’s plans publicly. Jordan also tested positive for the coronavirus last week and immediately ruled himself out of the restart. Chandler cited family reasons for not playing; Durant (Achilles’ tendon) and Irving (shoulder) are recovering from injuries.

The uncomfortable reality for the league, at the start of such a pivotal week, is that an increasing number of players have voiced apprehension about the restart, raising concerns that go beyond the coronavirus and injury risk — though the fact that at least seven of the 22 Disney-bound teams over the past two weeks closed their practice facilities at some point because of positive tests surely stoked concerns.

The Nets’ Garrett Temple, a vice president for the National Basketball Players Association, acknowledged in an interview Sunday that there’s considerable player anxiety about the challenges of living and playing on the Disney campus for at least six weeks, and potentially up to three months for the teams that reach the finals.

“I would imagine more than half of the league, of the players that are going, have had second thoughts,” Temple said Sunday, describing his own state as a “nervous anxiousness.”

Weltman, the Magic’s president, also acknowledged that the weight of “leaving your families and leaving your loved ones behind for such a long period of time” had been felt more acutely throughout his organization over “the last few days.”

Said Tilman Fertitta, the owner of the Houston Rockets, in an interview with CNBC: “If it ever becomes unhealthy, I promise you — the players, the owners and the N.B.A. office together will decide this isn’t the right thing. As soon as it becomes dangerous, I can promise you, we won’t do it.”

Sopan Deb contributed reporting.