sa

Some sage advice … Ricky Ponting chats with Mitchell Johnson during a training session at the WACA on Thursday. Photo: Getty Images

AUSTRALIA'S much-discussed fast bowling rotation policy has finally sprung into action, with Peter Siddle and Ben Hilfenhaus rested for the deciding Test against South Africa, despite the world No.1 ranking being up for grabs.

The result is an entirely new pace line-up for the third Test starting on Friday, and one that is likely to feature two debutants: Josh Hazlewood and John Hastings. The others in the 12-man squad captain Michael Clarke named on Thursday are Mitchell Starc and Mitchell Johnson, who are now set to become Australia's first left-armers to be chosen alongside one another since Johnson and Doug Bollinger in India more than two years ago.

Selectors had been armed with data from their sports science department that told them of the risk of playing Siddle in particular, given that he bowled more than 60 overs in Adelaide and the 142.5 overs he has sent down in total since the start of November.

Ultimately, they chose to sit out both the Victorian and Hilfenhaus, who was also forced into an excessive workload in the second Test, taking a caution-first approach despite the spoils on the line in Perth.

''It was a really tough decision, especially the way they've both performed, especially 'Sids' I guess, the way he performed in that last Test match,'' Clarke said. ''But we need to do what's best for the team.

''Pretty much we think both guys are still quite fatigued after Adelaide and we've selected that 12 to give ourselves the best chance of winning this third and final Test match against South Africa.''

On a wicket rated by WACA curator Cameron Sutherland as faster than it has appeared in domestic cricket this summer, Australia were leaning towards a four-man pace attack, as they did in defeating India inside three days here in January. Starc, the 12th man in Brisbane and Adelaide, is the only survivor from that occasion.

There is a recall for Johnson, nearly 12 months after he played his previous Test on Australia's tour of South Africa last November.

And in the absence of the injured James Pattinson and Patrick Cummins, selectors have turned to NSW seamer Hazlewood and Victoria's Hastings as the extra pieces to the bowling puzzle.

A debut on Friday would mark the culmination of a journey through serious injuries for 21-year-old Hazlewood. The Tamworth product played one-day cricket for Australia as a teenager during a series in England, and was chosen in a Test touring squad to India in 2010, before his body turned against him.

Sydney-born Hastings, 27, has been added as a result of an eye-catching start to the season for Victoria and would add valuable batting depth as well.

Clarke said having two debutants among Australia's fast bowling unit on Friday was not a concern.

''Not to me it's not .. and I don't think it's for the selectors either. I think they've both performed,'' he said. ''Josh has done really well for Australia in opportunities he's had and 'Hasto' is one of leading wicket-takers in Shield cricket at the moment so we're really confident.

''Like we said before we arrived, we've got a very good squad, we're really lucky, both guys are excited about opportunities to make Test debuts and we'll work out what the pitch is telling us tomorrow.''

The Proteas, meanwhile, are yet to make a call on the fitness of Jacques Kallis, who sustained a hamstring injury in Adelaide. They are hoping the all-rounder can bat - he has been ruled out of bowling - and if he does get the green light, it is likely that Jacques Rudolph will miss out on selection.

South Africa captain Graeme Smith is set to name four fast bowlers - Vernon Philander, missing in Adelaide with a back complaint - and a spinner, the left-arm orthodox Robin Petersen, not leg-spinner Imran Tahir.