Opening batsman Herschelle Gibbs is ready for South Africa's crunch World Cup Group B showdown with Sri Lanka on Monday, when he is determined to score his first one-day century at Kingsmead.

South Africa have to beat Sri Lanka if they are to qualify for the tournament's Super Six stage and the in-form Gibbs will be relied on heavily to get the innings off to a good start.

Regarded as one of the best one-day openers in the game, Gibbs has shone at this tournament, scoring 311 runs in five innings at an average of 103.66 and a strike rate of 106.14.

"I'm happy. I'm where I want to be mentally," Gibbs told reporters after South Africa's practice session was severely curtailed by rain in Durban on Saturday.

"I haven't got a one-day hundred here at Kingsmead yet so that becomes a target. I really wanted to go out and get a hundred at The Wanderers and I did that there (with 143 against New Zealand)."

Sri Lanka will call on the tournament's leading wicket-taker, Chaminda Vaas, to muffle the early fireworks by the South African opener, but Gibbs believes he is well equipped to combat the prodigious swing Vaas can generate.

"Against any swing bowler, your balance has got to be really good, especially early on when they do get that shape, your balance is crucial," he said.

POOR BALANACE

"I looked at the six wickets Vaas got against Bangladesh when he got that hat-trick and guys were just planting their foot -- their balance wasn't really that good."

Much has been made of the importance of winning the toss in day-night matches in Durban, but Gibbs believes there is little to choose between batting first or second.

He said it was far more important to target the Sri Lankans where they were weakest.

"The first few overs are really important here because of the bounce," he said.

"I watched the Sri Lankans yesterday (against the West Indies) and a few of their batters struggled against the short ball.

"I can't really speak from a bowling point of view but, if they are susceptible to one thing, it's short-pitched bowling. But you've still got to be able to land it in the right place.

"It's a bit of a farce all this talk about batting second. It's a really good wicket here and we've played enough cricket here under lights. We beat Australia here batting second and there's no reason we can't do the same on Monday."