With an unassailable 3-1 series lead up their sleeve, the Proteas will blood 19-year-old all-rounder Wayne Parnell and 24-year-old left-arm paceman Lonwabo Tsotsobe in place of Steyn and Ntini in their tour finale.

All-rounder Jacques Kallis, who is battling a side strain, will also be given the night off if left-handed batsman Vaughn van Jaarsveld can overcome an ankle injury, leaving South Africa to field one of its youngest sides ever.

In contrast Australia, in danger of losing the world No1 ranking, has recalled vice-captain Michael Clarke and swing bowler Nathan Bracken into the 13-man squad in place of Ryan Harris and Nathan Hauritz.

South Africa's bowling coach Vinnie Barnes admitted Ntini and Steyn would have played had the series been tied at two apiece.

But he scoffed at suggestions the visitors were treating the dead rubber as little more than a practice hit-out.

''We are looking long-term. We have to rest players, we are committed to that,'' Barnes said.

''We are not going to go into Friday's game thinking about losing or taking it as an ordinary game, there's a huge commitment from everybody.''

Clarke, who returns after missing the past three matches with a thumb injury, said it was important for Australia to get back to its winning ways ahead of its five-match one-day series against New Zealand, starting on Sunday.

''I guess we've been outplayed in this series to date,'' Clarke said.

''Come Friday it's an important game for us.

''We want to play good cricket, we want to come out here and play our traditional positive, aggressive cricket and hopefully take some momentum from this last one-dayer into the New Zealand series.''

The Proteas would leapfrog Australia into top spot in the one-day rankings with a win in Perth but Barnes said the game was more about creating momentum heading into next month's return Test series between the two countries in South Africa.

Clarke, who wore a protective glove during field training yesterday and also copped a blow to the groin while batting in the nets, said the prospect of Australia losing the No1 mantle had not played on the team's mind.

''I don't think it's for the players to worry about to be honest,'' Clarke said. AAP

TOMORROW

One-day series final game: Australia v South Africa at the WACA Ground, 3.30pm. TV Time: Live on WIN.