Clarke sounds World Cup warning for Australia after South Africa defeat

Australia got their tactics and team selection all wrong in Thursday's World Cup defeat by South Africa and the five-times champions must quickly get their act together if they are to avoid a group-stage exit, said former skipper Michael Clarke.

The 134-run loss in Lucknow marked a second straight defeat at the 50-overs showpiece and Clarke said things do not get any easier with Sri Lanka and Pakistan up next for Australia, who have failed to reach 200 runs in both games so far.

"I'm not saying our World Cup is over. We could still qualify with two losses, but Sri Lanka are going to be tough in those conditions. We haven't played Pakistan yet," Clarke told Sky Sports Radio.

"We've got some really tough cricket ahead of us and if we play like this, we are not qualifying. I'm more worried about the subcontinent teams.

"If we're getting shown up like that against South Africa, with the spin in the sub-continent teams ... we'll be laughable.

"If we're not careful the conversation we've been having for the last three weeks about the Wallabies, in two weeks' time we'll be having that about Australian cricket," said Clarke, who won the World Cup twice with Australia in 2007 and 2015.

The 42-year-old also said captain Pat Cummins "got it wrong" tactically.

"He won the toss and bowled, I think he ball-chased and I don't think he was aggressive enough. I don't think he looked to take wickets," he added.

"The easiest way to slow scoring is to take wickets yet we continue in Twenty20 cricket and one-day cricket, try to prevent runs. How is Cummins not bowling in the first 10 overs?

"I love him and I'm more than happy for him to be captain but he's got to do some work on that."

Clarke also criticised the decision to drop wicketkeeper Alex