Former Australia coach Darren Lehmann expects Steve Smith and David Warner to play a big role in their title defence on their return to international cricket at the World Cup.

Smith and Warner have returned from year-long bans following a ball-tampering scandal in South Africa which also prompted Lehmann to step down as coach of the side in March last year.

The top order duo made impressive return from elbow surgeries for their respective franchises at the Indian Premier League Twenty20 tournament and Lehmann was convinced they will shine at the World Cup in England and Wales.

“Smith at number three or four, he'd be exceptional at the World Cup,” Lehmann told Macquarie Sports Radio.

“People are worried about the break they've had with 12 months out, but you see them in the IPL performing and making runs.

“David Warner is an excitement machine, at the top of the order, he can set it alight.

"If he has a really good tournament, he set us on the road to winning a lot of games in the last World Cup. If he does it again at the top of the order with Aaron Finch, they'll be hard to stop."

Warner, who will never captain Australia for his role in the scandal in South Africa, looked particularly impressive at the IPL finishing as its leading scorer with 692 runs from 12 innings that included nine 50-plus scores.

In his absence, Finch and Usman Khawaja have formed a steady opening partnership for Australia but Lehmann expected Warner to slot back at the top of the order.

"Opening with Finch and Warner, I think that's a certainty," the former Australia all-rounder said.

"And then there's Khawaja or Shaun Marsh at three I'd think and Smith at four — this is your top four."