The first major test of how an Olympics can be held in the midst of a pandemic may well come this week in the men’s soccer tournament, when Japan face a South Africa side that could struggle to field 11 players due to the new coronavirus.

South Africa’s squad was severely depleted by COVID-19 infections and withdrawals before they left for the Games and was then hit with the news that two players and a video analyst had tested positive on arrival in Tokyo.

Twenty-one members of the delegation were close contacts, organisers said late on Monday, leaving South Africa walking a tightrope ahead of Thursday’s match against the hosts. The number was later reduced to 18.

The Olympic playbook on coronavirus prevention measures mandates that to compete a close contact must return daily negative PCR tests, including one within six hours of competition. They must also undergo a health check by an expert and receive permission from their international sporting federation.

FIFA regulations stipulate a team must have 13 available players for a match to go ahead. South Africa coach David Notoane said on Tuesday the daily testing means he has no idea who will be able to take the field to face the Japanese.

“You are not even sure who will be eligible for your (starting) 11 because of the situation we are in, testing every day,” he told reporters about the team, who returned to training on Monday after a week off the pitch.

The host team’s “physical readiness compared to us will be a key issue. It will make a huge difference. We basically lost seven days and that is hard to recover from.”

The Japanese men’s coach Hajime Moriyasu said his players remained unfazed by the news of coronavirus-positive cases among South African players.

“I don’t see anyone in my team shaken by this,” Moriyasu told a news conference. “I trust people involved will set up an environment where athletes can play safely and comfortably. So, we would like to focus on what we’ve got to do.”

Michiko Dohi, COVID-19 chief liaison officer with the Japan Olympic Committee, said that with the proper, strict steps being taken, the match could be held safely.

There have been 58 positive cases of Olympics-linked athletes, staff or officials recorded in Japan this month.

On Monday, a Czech beach volleyball player tested positive at the Olympic Village while an alternate for the U.S. women’s gymnastics team tested positive at the site of their pre-Games training camp just outside Tokyo.

Dohi said most of the positive cases had been contracted before the delegations entered Japan.

“My understanding is that they weren’t (caught) in the Olympic Village,” she told a news conference on Tuesday.