Ireland's presence as the only non-test team left in the competition is no surprise to Arthur and he has prepared his team as professionally as he would before any match, he said.
South Africa won their first Super Eights game against Sri Lanka last week and are one of the favourites to progress to the semi-finals. Ireland, a team of mostly amateurs, are expected to finish eighth and have already lost to England.
"This is the business end of the competition," Arthur told reporters. "You can't afford any slip-ups, so our preparation, training and mental training going into this game would have been the same as any game because it's a Super Eight.
'VERY CLINICAL'
"It's about getting two points but if we're very clinical and very good we will get those two points and I'm pretty sure we'll get them convincingly.
"This is all about a clinical South African performance much like the performances we put in place against Scotland and Holland (in the group stage)."
It is expected that left-arm spinner Robin Peterson will keep his place after Ireland's batsmen struggled against England's slow bowlers on the same ground on Friday.
Arthur also predicted a strong reaction from seam bowler Shaun Pollock after his bowling was surprisingly expensive in the last two matches.
Arthur said teams are now targeting opponents' best players but backed Pollock to respond positively.
Ireland, meantime, may be tempted into a rare team change as coach Adrian Birrell hinted that it is becoming "tricky" to manage players who are not playing.
The only time they made an alteration was against West Indies when captain Trent Johnston was injured.
"We've had four games and we've basically stuck to the same team so it's getting harder and harder on those guys," said Birrell, who goes up against his countryman and friend Arthur.
"We've only played 12 players and it's something I'm aware of. It does get a bit more tricky as time goes on if players are not playing."
