A pace shootout capable of inspiring a generation, and the world's two best Test teams operating on a pitch that won't make day four.

Some of it hyperbole. Some of it true.

Tonight, it'll be easier to separate the two when the talking ends and Australia's much-anticipated three-Test series in South Africa starts on a green Centurion pitch expected to offer Gabba-like bounce.

The Proteas' iron-clad grip on No 1 spot in the ICC's Test rankings is assured. Even if the No 3-ranked visitors pull off an unthinkable 3-0 sweep, they will rise only to second.

Unthinkable is generous.

Australia are not confronting a brittle English side, rather a dominant force that has conquered everything in its path since rolling into the UK in 2012 and leaving with the best-in-the-world mantle.

They haven't lost a Test series away since Sri Lanka in 2006, while Australia inflicted their most recent Test series loss at home in 2009.

Unprompted, Australian skipper Michael Clarke compares the Proteas to the side he joined on Test debut in 2004.

"That's a fantastic achievement," Clarke said.

"They have been able to perform consistently at home and away over a long period of time, a little bit like the Australian team that I first walked into.

"The reason we were No 1 for so long was because we had as much success away from home as we did at home.

"That's now our greatest challenge as a team."

It's a challenge made more difficult due to a rain-interrupted preparation, while Shane Watson's calf injury and George Bailey's axing mean two new faces come into a team that was unchanged throughout the Australian summer.

"It's about adapting ... I can guarantee you there was a lot of stuff in the lead-up to the First [Ashes] Test in Brisbane that wasn't perfect," Clarke said.

Alex Doolan is expected to debut at No 3 in place of Watson.

Phillip Hughes and Shaun Marsh batted in tandem in a nets session on Monday, while the pair also took turns fielding in the slips at training.

All-rounder Moises Henriques is also a chance of claiming the final spot ahead of Hughes and Marsh.

The Proteas start strong favourites at a ground where they've won 14 of 18 Tests.

Ryan McLaren is tipped to replace retired champion Jacques Kallis, while Faf du Plessis will rise to No 4 in a reshuffled batting order.

Clarke agreed Kallis's absence will help his cause, but noted batting depth wasn't exactly the hosts' weakness.

"You get Graeme Smith out and Hashim Amla comes in. You get Amla out and AB de Villiers - No 1 batsman in the world - is in."

Their bowling is arguably better. Vernon Philander and Dale Steyn sit No 1 and No 2 on the ICC's Test rankings.

And their battle with Mitchell Johnson, Ryan Harris and Peter Siddle has dominated the build-up to the match.

As has the hype surrounding Johnson's spectacular Test career resurrection, and Clarke was keen to point out "one bowler didn't win us the Ashes series".

Clarke was cautious about weighing into the pace debate further, saying Australia's top order will be facing up to a "magnificent" attack. AAP