Sale Sharks owner Brian Kennedy said he 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.
American tycoon Miller was handed preferred bidder status last Thursday ahead of a rival bid from Kennedy and the Blue Knights consortium, but he has now 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 - but he told the Daily Record: "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."
He continued: "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.
"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."
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."