Ally McCoist’s side lost 2-1 away to Dundee United- their third SPL defeat in four matches- to leave themselves 21 points behind Celtic.
An away win at Ibrox next Sunday would take Celtic 24 points clear of their city rivals with just seven games left to play.
Motherwell would still be able to catch Celtic if they win their next two matches, at home to Aberdeen and away to Kilmarnock.
Despite avoiding making any players redundant Rangers were unable to get back to winning ways at Tannadice.
Keith Watson and Jon Daly put the home side 2-0 up with goals either side of half-time before a cross from Sone Aluko was deflected past Dusan Pernis but the visitors were unable to salvage a point.
In 36 games in charge of Rangers McCoist has tasted defeat 9 times.
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