The N.F.L. will announce its schedule for the upcoming season on Thursday night in a prime time TV event. But a handful of teams have begun tempering expectations that fans will be able to attend some of those games — assuming they will be played in front of fans at all.

On Wednesday night, the Jets franchise announced that it would not be selling single-game tickets after the release of the schedule.

“Given the changing conditions surrounding the Covid-19 pandemic, individual game tickets will not go on sale tomorrow,” the team announced in a statement posted to Twitter. “We believe this is the prudent thing do to in order to provide the best experience and service for our fans at this time.”

That the Jets are forgoing the opportunity to sell tickets when hope for the new season is high just two weeks after the draft suggests that teams are slowly tinkering with their normal procedures as they adjust to business during a pandemic.

The Jets’ cautionary announcement came just a day after N.F.L. Commissioner Roger Goodell told all 32 teams that they need to have a ticket refund policy in case games are canceled or fans are prohibited from attending games, according to a memo obtained by The Associated Press. Fans, Goodell said, will have the choice of getting a full refund or getting a credit for tickets they can buy in the future.

The memo was another sign that the league has had to walk back its statements in March, when N.F.L. executives said they were planning for a full slate of games with fans in the stadiums starting as scheduled in September. As the coronavirus has continued to spread, including in cities where N.F.L. teams operate, the league has been forced to adapt.

While it forged ahead with free agency in March and the N.F.L. draft last month, the selection of college players was done remotely, not before tens of thousands of fans in Las Vegas, as had been planned. Team facilities have been closed since mid-March, forcing teams to hold off-season workouts and meetings with players entirely online.

The N.F.L.’s opening game is not scheduled until Sept. 10, so it has the luxury of time to prepare rather than have its season interrupted as other leagues were. The N.B.A. and N.H.L., for example, were forced to shut down a month before their playoffs were set to begin.

But given the persistent spread of the virus, which infects tens of thousands of Americans each week, some infectious disease experts believe leagues like the N.F.L. may have to play games without fans in stadiums to start on time and to limit the risk of exponentially spreading the virus.

“I’m not saying this is the way to go, but you want to at least consider to have players, if they’re going to play, to play in front of a TV camera without people in the audience,” Dr. Anthony S. Fauci, the leading public health expert on President Trump’s coronavirus task force, told The New York Times last week. “If you can do it with some degree of confidence in the broad general safety of both the players and the fans, if you are going to have fans — if you have TV you don’t have to worry about it — but if you’re going to have fans, that has to be the prevailing, dominating theme: the safety of the people involved.”

According to an N.F.L. spokesman, about three-quarters of the league’s 32 teams are selling, or expect to sell, single-game tickets. The Jets appear to be the first team to publicly state that they will not sell single-game tickets. Giants officials, when reached for comment, said that no decision had been made about ticket sales. Other teams, like the Falcons, do not sell single-game tickets, only season tickets to fans who hold personal seat licenses.

Of course, fans across the country can buy tickets from ticket resellers like Ticketmaster and StubHub. Many of those tickets are posted for re-sale by season ticket holders. Other teams are bracing for a season in which social distancing guidelines limit the number of fans in stadiums.

On Monday, Tom Garfinkel, the president of the Miami Dolphins, said games at Hard Rock Stadium could include just 15,000 fans this season, about one-quarter the building’s maximum capacity.

“We would have times to come in for security at different gates so people would be separated out in terms of when they enter the stadium,” Garfinkel said on “Good Morning America.” “We would exit the stadium much like a church environment, where each row exits so people aren’t filing out all at the same time in a herd.”