Proteas bowling coach Charl Langeveldt said forcing Australia's top six to play very early in their innings will be crucial to their success in the forthcoming Test series that starts on Saturday in Brisbane.In their 2-0 Frank Worrell Trophy series win against the West Indies, Australia's top six, ably marshalled by Marnus Labuschagne, displayed excellent patience before grounding the Windies into dust.Labuschagne, who has made nine of his 10 Test hundreds in Australia, made scores of 204, 104*, and 163 in the West Indian pummelling.READ | De Bruyn hopes for Proteas return in 'Holy Grail' Aussie series: 'I feel really privileged'Steve Smith stands as the biggest threat and one with the most to prove against South Africa, with the former Test captain only averaging 41.53 (his second-lowest against the Test nations he's played against) and without a Test century against the Proteas at home.Smith made 200*, 20*, 0 and 35 against the West Indies while opener Usman Khawaja goes into the series with scores of 62, 65, 45 and 6 against the West Indies.David Warner (5, 48, 21 and 21) is under the harshest microscope despite his excellent record against South Africa (1 202 runs at 52.26) home and away.Langeveldt made it clear that Australia's top six, which also includes Travis Head, needs to be targeted early.Australia weren't bowled out in all four of their innings against the West Indies. "The key to their top six is the first 20 balls," Langeveldt said."We have to make them play and Steven doesn't move a lot.
He's got a good base now and doesn't move around the crease."It's going to be a big challenge for our boys, and they'll be up for it, but the key is the first 20 balls.