Gordon Smith reckons it's win or bust for Rangers tomorrow afternoon in their crunch derby clash with rivals Celtic at Parkhead.

Gers go into the action already five points adrift in second place, albeit with a game in hand after Celts played an extra match against Hearts earlier this month.

An eight point lead would be insurmountable, according to ex-Light Blues star Smith.

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But that's what faces his former club if they fail to walk out of the Celtic Park cauldron with a victory.

"This is a must-win game for Rangers when they go to Celtic Park," Smith said.

"They can't afford to lose it or the league title becomes a very, very difficult thing for them to win.

"Rangers need the points and Celtic have played an extra game in the league in December. 

"If they beat Rangers it would then be an eight-point gap.

"If Celtic get an eight-point gap at that stage, you'd have to say they would be massive favourites.

"This game is crucial, absolutely crucial. If you look to anyone at Rangers they'd say what they want is the league title."