The number three batsman's skills to anchor an innings would be crucial if South Africa are to end their semi-final jinx on Wednesday by upsetting holders Australia, who have been unbeaten for 27 World Cup matches going back to 1999.
Kallis, who heads the rankings for test all-rounders and is only behind team mate Shaun Pollock in the ODI list, is his country's leading one-day run-scorer and reached 9,000 runs in the Super Eights win over England.
At this tournament, he is the joint second highest run-getter with Australian skipper Ricky Ponting; their tally of 480 runs is only behind Australian opener Matthew Hayden.
However, the 31-year-old Cape Town player has faced criticism that he scores those runs at too slow a pace for the limited overs game.
Skipper Graeme Smith, however, said Kallis had tweaked his one-day approach.
"Jacques is a world class player and he definitely is a team player," Smith told reporters. "He bats the way he assesses the conditions, the team total on that day.
"He has won many games for South Africa as a batter and he still will win many.
"Certainly over the last couple of months and over a year he has had a look at his one-day game and maybe with the game changing he has had to reassess a few things.
'TURN SCREW'
"I'm sure he is going to play a massive role in the semi-final. I hope he is one of them who can turn the screw."
Kallis was questioned when he made 48 from 63 balls in the 83-run defeat against Australia in a group match after Smith and AB de Villiers had scored racy fifties in chasing the champions' huge total of 377.
Kallis was dismissive when he was slated for being a selfish batsman.
"Not at all," he said. "You are used to criticism over your career.
"It is just another game of cricket. I'm going to approach the game the way I approach any other game."
However, the well-built player is already responding.
The South African vice-captain, in his fourth World Cup, has a strike rate of 84.35 in the tournament which is a big jump from his career mark of just over 70.
Kallis, like Herschelle Gibbs, Pollock and wicketkeeper Mark Boucher are hoping to avenge their 1999 tournament exit after the semi-final against Australia was tied.
Having sealed their last-four place with a crushing nine-wicket victory over England in their final second-round match, Kallis was confident the South Africans would maintain their winning momentum.
"We've had ups and downs," Kallis said. "Perhaps we haven't played consistent cricket we would have loved.
"We will take the confidence out of the last game and hopefully we've peaked at the right time."
South African fans would be praying Kallis would step it up at the right time.
