Rangers' woes continue after they went down 2-1 to Dundee United in their Scottish Premier League clash at Tannadice.
United defender Keith Watson's first-half strike and a Jon Daly goal soon after the break had the home side looking comfortable.
However, a deflected strike by Rangers substitute Sone Aluko off John Rankin, on for debutant Andrew Mitchell, brought the crisis-hit visitors back into the game but it proved to be a mere consolation.
Steven Hammell's wonderful long-range effort earned Motherwell a 1-0 victory over Aberdeen at Fir Park.
Hammell netted his second goal of the season after 22 minutes when he rocketed the ball beyond Jason Brown after collecting Tom Hateley's pass.
Victory for the Fir Park side moves them level on points with second-placed Rangers, although the Clydesdale Bank Premier League champions have a better goal difference.
St Mirren's hopes of a top-six finish were all but killed off with a 3-0 home defeat to St Johnstone.
Goals from Lee Croft, David McCracken and Fran Sandaza kept Steve Lomas' side joint-fourth with Dundee United in the race for a European place.
Danny Lennon's side remain eight points behind sixth-placed Hearts with just three game remaining before the split.