Gloucester chief executive Lance Bradley warns that the English professional game will be forced into making radical changes if fans are shut out of matches for an additional six months.
Concern over a second wave of coronavirus infections has resulted in plans for supporters to attend sports venues in England from October 1 to be placed on hold as part of additional new restrictions announced by Prime Minister Boris Johnson.
Johnson added that the new measures would remain in place for "perhaps six months".
Bradley fears that continuing to stage games behind closed doors would have dire financial implications, causing upheaval.
"I don't want to sound over-dramatic but it can't be for six months if we want to have professional rugby survive in the format that we know," Bradley told the PA news agency.
"At Gloucester we had plans for when fans would come back and we planned for some to be back at the start of the new season and for more to be back come January.
"It's a big problem for us not to have fans in grounds because it's about a third of our income.
"It's been painful but we can manage that. But there are clubs in worse positions than us. And if there were an extended period with no fans then that would be very serious.
"I don't want to say this club or that club would definitely go out of business, but it would prove to be a hugely challenging time if there were no fans for six months.
"We can't just shut everything down for six months. If we're not allowed to have fans for an extended period, then some kind of financial support to overcome that would certainly help.
"But what we would far rather do is work with the government to make sure we actually get fans in.
"The objective isn't just to contain the virus, it's also to have something to come back to afterwards and if we don't let fans into Premiership grounds, football grounds, cinemas and theatres, they are not going to survive."
Bradley's view was echoed by Saracens director of rugby Mark McCall, who believes the bleak outlook caused by continuing to play behind close doors will extend into the Test arena.
"It doesn't take a genius to guess that if England don't get crowds during the autumn and the Premiership don't start having crowds before Christmas, it's going to be a really worrying time," McCall said.
"That will be for the international scene and also the club level. It's obviously very serious. Everyone needs fans in to get some revenue.
"For that to be delayed again until no one knows exactly when, that's very worrying."
Bristol director of rugby Pat Lam insists the reverberations felt from the new measures would be felt across the Premiership.
"Without a doubt, it will have a huge impact on the whole industry if fans aren't coming in. It will certainly be tough for us, but it's the same for everybody," the Bears boss said.
"We're a business and having fans attend games is a core part of our business. Not having them there is a huge loss for clubs and has a big impact on the financial side of it."
