Sale Sharks owner Brian Kennedy will "reflect on his own position" after expressing fears over the future of Rangers following Bill Miller's decision to withdraw his offer for the club on Tuesday.
American tycoon Miller was handed preferred bidder status last Thursday ahead of a rival bid from Kennedy and the Blue Knights consortium but has informed administrators he will not pursue his interest any further.
Duff and Phelps are now evaluating three other bids for the Glasgow giants - which does not yet include a fresh offer from Kennedy.
Kennedy told the Daily Record: "Words fail me. All my worst fears are coming to pass. In the meantime, I am reflecting on my own position.
"I'm not trying to be a smart ass here. This was a clear sequence of events. I could see it, every Rangers supporter could see it was likely to unfold.
"And yet here we are, in an even more perilous position than ever. My worst fear is that we could see a padlock on the gates of Ibrox."
Kennedy added: "I don't give a monkey's about the Americans pulling out. I care about the damage that has been done in between and where it will all lead to.
"When someone predicts a sequence of events 'A, B, C, D and E', and when 'A, B, C, D' happens then you've got to think there is a good chance 'E' will happen too.
"If anyone is going to step up and do something then they'd better do it soon. I will reflect on this and will be talking to those who were considering investing with me."
Andy Kerr, president of the Rangers Supporters Assembly, urged Duff and Phelps to "move with the utmost haste" to secure the club's future.
He told BBC Radio Scotland's Good Morning Scotland programme: "Let's be open, let's be honest, let's fully understand another false dawn is going to be the final nail in the coffin."
Asked if the game was up for Rangers, he replied: "I don't think it is up but we are in a critical situation and things need to happen very, very quickly.
"I very strongly urge Duff and Phelps and the people they are currently speaking to to move with the utmost haste now."
Miller said preliminary information he had received about the club was "more optimistic than reality", and also made reference to opposition to his takeover bid by Rangers supporters.
One of his advisors, Club 9 Sports chief executive Jon Pritchett, said the businessman received "vitriolic" emails from fans.
Referring to the emails, Kerr said: "It would be interesting to see one or two examples and just try and understand what sort of people were doing that.
"We saw a couple of banners and we're talking about a few people here, and it is disappointing when people are effectively prejudging the guy.
"The general call from the supporters was, 'Who are you? Give us an explanation of what you are trying to achieve. Let's try and work together and engage with you and see if we can take the club forward'. That's where we wanted to be."
He added: "I just don't think that he had an understanding of the business, what was going to be involved to turn the club round, the precarious nature of where we are and where we're trying to get to.
"It just seems an odd scenario that someone from so far away was trying to buy into a 140-year-old institution."