Former US Open winner Marin Cilic feels the tournament will be devalued if it's played behind closed doors.
His 2014 triumph at Flushing Meadows remains his career highlight, but the Croat says staging the grand slam in front of empty stands would warrant an asterisk beside this year's victors.
US Open organisers are still planning to stage the tournament as planned, starting from August 31.
However, with New York badly hit by the COVID-19 crisis and the USTA Billie Jean King National Tennis Centre has been used as temporary hospital space.
Nearly 23,000 people in New York State have lost their lives because of coronavirus, with 15,789 concentrated in New York City.
This year's Wimbledon Championships have been cancelled, and the French Open pushed back to September.
That means the US Open will be the second slam of the year, and not the last as would ordinarily be the case.
Organisers are discussing a range of options for playing the tournament, including switching venues to Indian Wells, California.
For Cilic, playing behind closed doors is not an option.
"I just feel that it’s going to more or less feel like practice matches", the current world no.37 told Reuters.
"It’s always going to be... in the years to come, ‘oh, you know that guy won a U.S. Open in 2020 without fans’. I don’t think it’s going to have that weight...
"It wouldn’t be the best scenario."
Tennis on both the ATP and WTA tours is suspended until July 31 at the earliest.
But where football seasons are in races against time to finish before the start of September, Cilic believes tennis has time to play with.
"Tennis season is slightly different than football, than basketball," he added.
"They have seasons to finish off, and the next season is depending on this season as well. For tennis, if we start in December or in January, it’s not going to change too much.
"I believe that there won’t be any tournaments without fans.
"Basically the whole tour is revolving a lot on sponsors and people coming to the tournaments.
"Sponsors are investing money because people are coming to watch tennis and see the players."