Cilic, who held the trophy aloft at Flushing Meadows in 2014 in the biggest achievement of his career, felt a crowd-free environment would devalue the accomplishment.
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"I just feel that it's going to more or less feel like practice matches," the former world number three told Reuters in an interview from Croatia.
"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."
Cilic thinks the international travel required to get professional tennis up and running again means the issue might end up being academic in any case.
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"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."
While many players have been left with a lot of spare time and an empty schedule during the shutdown, the break has proved timely for Cilic, who became a parent for the first time in January.
The 2017 Wimbledon and 2018 Australian Open finalist said his entire day locked down on the coast of the Adriatic Sea revolved around his son 'Balbo'.
"It is a very, very big blessing for me. It's a silver lining situation," the 31-year-old said.
"Basically since his birth I have missed only two weeks of his life. It's been a beautiful time with him, spending time with my family, seeing how he's growing up and then feeling all the things that he is going through.
"It's been, I have to say, one of the best moments and best periods of my life, of my tennis career."
While Cilic is in a much better mental state than some of his tennis colleagues, he says he might also have a physical advantage when the circuit finally resumes.
"I was really privileged as we moved to my wife's hometown, which is quite a small place," he said.
"I know a person that runs a couple of tennis courts here and he gave me keys to one. So we were able to play on our own, me and my coach.
"I believe, more or less, when things become calmer everyone is going to have enough time to prepare and train but hopefully I'm going to be just slightly better."