Harpur said: "I have waited my chance patiently and have confidence in my ability so I will have no problems with what will come my way.
"The last time I played in the first team other than trials was just before I came to Britain. It was the ABSA Cup Final and we got 85,000 fans to that.
"It was a big occasion there. It was a hostile crowd and the fans are hostile throughout South Africa because they love their football.
"They let you know they are around when their team is on top. That can be quite daunting but I am sure it will be no different on Saturday.
"It is nothing like playing Celtic which is something you dream of all your life.
"I am looking forward to it. It is a little daunting but it is a game that everyone wants to play and I am no different.
"If given my chance I will do my best to get a memorable result. I'm looking forward to it greatly."
Harpur will come in from the freezing cold as No.1 Alan Combe is struggling to be fit because of a calf injury.
The keeper, who joined Kilmarnock in August 2006, was set to make his debut against Airdrie in the Scottish Cup but the tie was postponed because of a frozen pitch.
Jefferies has no problems putting him in but Harpur thinks he is right not to mention anything to him.
He said: "The manager has been quite quiet about it.
"He gives encouragement to you and lets you get on with your own thing and lets me prepare in my own way.
"If he said anything it would make me worry even more and he knows that."
Harpur had unsuccessful spells with Leeds and Millwall but has no complaints with being the understudy to Combe, who he thinks should be a regular in the Scotland squads.
He said: "Alan has been absolutely superb and if a player is playing that well you have to wait your chance and take it when it comes.
"I learn from Alan every day. His professionalism is great.
"He could be playing at a much higher level and I am surprised he hasn't been called into more Scotland set-ups."
Harpur is convinced he can handle anything Celtic and Shunsuke Nakamura throw at him.
He said: "We know if we can keep it tight and nick a goal, anything can happen.
"Nakamura is back just in time, isn't he? He scored a great goal at the weekend and that shows his quality.
"But I take everything in my stride and keep calm. If you start thinking about it then you could worry yourself to death."