The Scottish champions headed into the rearranged clash at McDiarmid Park hoping to extend their lead at the summit to 13 points and take another step closer to retaining the title.

Instead, a stunning show from Saints saw the Perth side bolster their hopes of a top six finish and Smith is expecting better from his players when they host Hamilton at the weekend.

He said: "We've not taken that many defeats and we have always had a good reaction from our group overall.

"Certainly we will have to get a good reaction from them on Saturday.

"All the games are important and performances are important. Tonight, in the first half especially, it wasn't good enough.

"I thought St Johnstone were excellent in the first half and I'm disappointed that my team didn't match that."

Goals from Cillian Sheridan, Chris Millar, Liam Craig and Murray Davidson secured the points for Saints, with a Sasa Papac strike scant consolation for Rangers.

It was the first time the Ibrox side had conceded four goals outside an Old Firm derby since a 4-2 defeat at Hearts back in September 2007.

Smith added: "We don't seem to lose two goals or anything like that. We seem to go from not losing any or losing one to losing three or four.

"They were poor goals tonight from our point of view and St Johnstone will be happy with the manner in which they got their goals."

However, Smith did not feel complacency had a part to play.

"I don't think so," he said.

"I don't take anything away from the way St Johnstone played tonight. They set about the game well as the majority of teams do against us at any given time in the year but normally we have a better reaction to that.

"Tonight we lost a couple of poor goals defensively but you can't take anything away from St Johnstone - they were brighter and more aggressive than we were.

"The disappointing thing was that they are striving to get into the top six and we are striving for the championship but they looked keener and were more aggressive than we were in the first half of the game."

Saints have run Rangers close in the past and boss Derek McInnes was always confident in their ability to claim a win over the champions-elect.

But he admits even he was surprised by the emphatic nature of the victory over his former team.

He said: "You've got to enjoy nights like this. We had a poor defeat to Hamilton at the weekend and we always seem to respond to a poor result.

"But to do so so convincingly, I wouldn't have thought we would have won by that scoreline.

"We had a lot of top performances and it would be wrong to single anyone out. We played with a lot of intelligence and the players deserve all the credit in the world."