MELBOURNE: The prospect of a rain-interrupted start to the Hobart test has South Africa mulling a four-pronged pace assault to push for a series-sealing win over Australia when the match begins on Saturday.

South Africa routed the home side by 177 runs in Perth with just two fast bowlers and debutant spinner Keshav Maharaj after pace spearhead Dale Steyn was injured when bowling in Australia's first innings.

Left-armer Maharaj took four wickets in a successful debut at the WACA but may be rested at Bellerive Oval as Faf du Plessis' side bid for an unassailable 2-0 lead in the three-match series.

"There is a possibility of that," Du Plessis told reporters in Hobart on Friday. "If it becomes a really shortened game ... that's something we will look at.

"It looks like there's going to be a little bit of rain tomorrow, so if it rains for the whole day it becomes a four-day game.

"The pitch is going to be under covers, the ball is going to be wet."

Heavy rain is forecast for the opening two days of the test, which could frustrate both sides' hopes of victory.

South Africa have Morne Morkel and Kyle Abbott vying to replace Steyn, who suffered a fracture in his shoulder and could be out of the game for more than six months.

Towering seamer Morkel was left out of the test in Perth as he recovers from a back injury that has sidelined him for two months and coach Russell Domingo said they would need to test his fitness again before making a call on the side for Hobart.

Du Plessis gave no clue which quick was favoured, but Abbott may have the edge for Hobart's heavier wicket which could mean long spells for the pace bowlers.

"We'd like to see the conditions," said Du Plessis.

"(Australia) are in the same boat as us. You just want to make sure you pick the strongest team for the conditions."

Australia have also held off naming their starting side but Steve Smith earlier poured cold water on the notion of dropping regular spinner Nathan Lyon in a favour of unleashing four quicks.

"I'm not really sure that's the way we're thinking," he told reporters.