South Africa looks likely to leave out struggling strike bowler Makhaya Ntini for its ICC CWC semi-final against defending champion Australia today.

Coach Mickey Arthur said on Tuesday it would be tough to change the XI that beat England by nine wickets in its final Super Eight game to qualify last Tuesday.

Ntini, 29, was axed for that match after taking only six wickets in seven games at 48.83 runs apiece on pitches unhelpful to his in-swing bowling.

"I'd have thought we would go in with 12 and then make a final decision," he said.

"We'd have a look at the spinner (Robin Peterson) in the 12 and make that decision tomorrow."

The pitch at the Beausejour stadium is expected to favour batsmen.

Ntini, who joined the South Africa party late because of the birth of his second child, has struggled throughout the tournament for form.

The Proteas' concerns over skipper Graeme Smith's knee injury, though, have eased, Arthur added.

"We are full of confidence he will be 100 per cent tomorrow."

Australia, bidding for an unprecedented third title in a row, hold the upper hand after their 83-run group stage win over South Africa in St Kitts on March 24.

"We've picked up some trends (skipper Ricky) Ponting used during that game," Arthur said.

"The area where we weren't fully on the mark in St Kitts, we allowed Australia to put us under pressure."

Opening batsman Matthew Hayden hit the fastest hundred in ICC CWC history to help amass 377 on a small ground before Australia ended a 160-run opening partnership between Smith and AB de Villiers to set up victory.

The South Africa players have maintained focus, according to Arthur, unlike in the past when they have been dubbed Cup chokers for succumbing to pressure.

The contest is a repeat of the 1999 semi-final where eventual winner Australia forced a dramatic tie and went through, having won its second-round clash.

"I haven't been involved with this team, leading up to a game of this magnitude. I haven't seen the guys so calm," Arthur said.

"That is the way you have got to go into a game like this.

"I don't want the guys to be waking up in the middle of the night thinking Cup semi-final."

The final of the seven-week tournament is at the Kensington Oval, Bridgetown, Barbados on Saturday.