Rangers beat St Mirren 1-0 to delay Celtic's title celebrations for at least another fortnight. Celtic, who beat Motherwell 1-0 yesterday, need another three points to clinch their 41st Scottish Premier League title.
With five matches remaining, Celtic have 78 points from 33 games, 13 more than second-placed Rangers who occupy the second Champions League slot.
Striker Nacho Novo hit the winner for Rangers in the fourth minute as Saints keeper Chris Smith came for a long, diagonal ball into the box from Charlie Adam and failed to collect under pressure.
Novo pounced six yards out and rifled a shot off defender John Potter into the middle of the net.
"It was a kind of fraught afternoon and the first time this season for the bumpy pitches," Rangers manager Walter Smith said.
"We had to work very hard to hold them out and managed to do so. It wasn't pretty for either side. . .but I am just pleased that we won it."
Rangers striker Kris Boyd passed up two fine first half chances to seal the game by hurrying a 20-yard shot and blazing over on 31 minutes, then moments later he fired a tame 15 yard effort straight at the keeper.
Boyd hooked the ball into the net from an Adam free-kick just before the hour only to be ruled offside and substitute Dado Prso dragged the ball across keeper Smith only to run out of room.
There are no league fixtures next weekend.