Ryan Rickelton's unbeaten 176 has put South Africa in a strong position following the first day of the second Test against Pakistan - and given Australia a taste of what could await should they play the Proteas in the World Test Championship final.

The left-handed opener was outstanding, batting all day on Friday as South Africa reached 4-316 at the close at Newlands and making his highest Test score during a partnership of 235 with captain Temba Bavuma (106) for the fourth wicket.

"We knew the wicket was playing well and if we could lock in with a partnership and stretch things out, that was always going to be important," Rickelton told reporters.

"Probably the same tomorrow against the new ball. I feel the wicket is brittle and dry underneath so I do anticipate turn later on. First-innings runs are always important, so we have to try and maximise them."

Rickelton, 28, and provincial teammate Bavuma know each other well and were a calming influence on one another.

"We bat really well together," Rickelton said. "We don't talk a lot in all honesty, he just emphasised doing the basics for long periods of time. He has been playing incredibly well recently.

"I naturally score quite quickly and once I was able to take some dismissals out of the equation, I could expand as the game allowed. I did not have to go looking for too much.

"I am bloody chuffed to be honest, a New Year's Test century in Cape Town is something you dream of."

Rickelton has batted everywhere from three to six in the South African order, but this was his first time opening the innings, forced into the role by an injury to Tony de Zorzi.

He says he had no hesitation when coach Shukri Conrad asked him to take on the new ball.

"Shukri spoke to me yesterday and said he would not put me into a position he did not think I could handle. I just want to bat, it doesn't matter where.

"I have trained a lot against the new ball, but mentally it is a big challenge and days like today are few and far between."

The left-hander's first Test century came last month against Sri Lanka and he says it was contrasting emotions between the two.

"Last time it was relief, this one was a bit more enjoyment. I had fun out there and played more how I like to play the game."

South Africa have already sealed a place in June's World Test Championship final at Lord's with victory over Pakistan by two wickets in the opening Test in the series, and look poised to face champions Australia, who are favourites to book the other spot.