Rangers' administrators aim to have new owners in place by the end of the season after receiving a fifth bid for the club.
Duff and Phelps are believed to have received an offer from a Singapore-based consortium.
They follow offers from former Ibrox director Paul Murray's `Blue Knights' consortium, Sale Sharks owner Brian Kennedy, a US-based consortium reported to be Club 9 Sports, and another unknown group.
Paul Clark, Rangers' joint administrator, told Sunday newspapers: "What we want to do is analyse the bids and I would suggest we will be moving to a shortlist that might be two or three bidders at some point next week.
"Our preference would be for somebody else to be in control of the football club other than us by the end of the season so they have got the whole close season, the whole transfer window, they have got proper preparation for the new season."