Bowling coach Allan Donald has labelled the current South African attack the best the nation has produced - even better than the pace battery he once led with devastating effect the world over.

Led by Dale Steyn and Vernon Philander - rated the top two bowlers in Test cricket - and supported by Morne Morkel, the South Africans have arrived in Australia with an attack sure to test a local batting line-up with more than a few question marks.

Alongside former Proteas skipper Shaun Pollock and the likes of Fanie de Villiers and Makhaya Ntini, Donald was once the leader of one of Test cricket's most feared bowling line-ups following their return to the fold in the 1990s.

But the ex-speedster was forced to bow to the current crop, who have helped elevate South Africa to the top of the Test rankings.

"I would have to say that, yes," Donald said.

"I'm not just saying that, because I was part of an attack with Shaun Pollock and myself and a few others, and I say that humbly and respectfully, I think this is as good as it gets."

That's ominous news for an Australian batting line-up which will head to the Gabba for the first Test far from secure.

The opening combination of David Warner and Ed Cowan have yet to convince they are long-term options, while it was less than a year ago that former skipper Ricky Ponting was hanging onto his spot by the barest of threads.

Donald said the South African attack's greatest asset was its ability to work as a group.

"They've been bowling together for quite some time," Donald said.

"Momentum's been built over the past couple of years, consistency in selection and it's nice to have a group of guys that know what they're about."

Veteran all-rounder Jacques Kallis (flu) did not train on Tuesday, but Donald expected him to be available for selection for the three-day tour game against Australia A starting at the SCG on Friday.

Wicketkeeper AB de Villiers also eased doubts over his availability as he took part in the session at the SCG nets without showing any lingering effects of the back injury which forced him to miss the recently completed T20 Champions League.