Australia's coach Justin Langer has labelled Shaun Marsh a "very, very explosive player" while insisting Usman Khawaja has the ability to adapt to a new batting role in the midst of the World Cup, after the selectors chose to leave middle-order specialists Peter Handscomb and Ashton Turner at home.

Marsh and Khawaja found themselves thrust into unfamiliar territory against Pakistan, batting at Nos. 5 and 6 after being given a superb platform by Aaron Finch and David Warner. Their struggles to play the innings required were part of Australia's rapid decline from 146 without loss to 307 all out at Taunton, after they had also faced batting issues against West Indies and India.

Before this tournament, Khawaja had never batted below No. 3 in ODIs, having entered the event as the world's leading 50-over run-maker in 2019. While debate has continued over the composition of Australia's World Cup 15, with the significant contributions of Handscomb and Turner overlooked to stockpile the squad with top order batting, Langer insisted that Marsh had the hitting power to match the likes of Jos Buttler and MS Dhoni among the rest of the world's best.

"[Shaun Marsh] is an unbelievable T20 cricketer - if you look at his T20 record, it's unbelievable. And I thought Uzzie played really well, like he adapted against West Indies the other day. It was a really different role for him. But I thought he did a good job," Langer said. "Both of them got out - for them and for us - just at the wrong time. They both showed some good signs.

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"Shaun Marsh is a very, very explosive player. I remember seeing him hit 28 [27] off an over in the semi-final. You've got to be pretty explosive to hit 28 off an over. He's been an incredible player for the Scorchers in Big Bash cricket, he's a very explosive player. It's exciting having him anywhere in the order and he can hit the ball as hard and as far as anyone in the world. And Uzzie does it his way."

As for Khawaja, Langer indicated that he needed to adapt to his new responsibilities within the tournament, although it also appears increasingly likely that should the Australians resort to an allrounder - either a fit-again Marcus Stoinis or Mitchell Marsh - it will be Khawaja who makes way after Steven Smith was promoted to No. 3.

"That comes with experience. He is used to batting at the top of the order," Langer said about whether Khawaja could make the changes necessary to fit into the side. "When you go in [later] there's different pressures. In a lot of ways, it's an easier time. It's an older ball and there's lot of gaps in the field. He'll adapt. And there will be times when he comes on the second ball of the day. I hope it doesn't happen, but he might."

Glenn Maxwell's promotion to No. 4 resulted in a rapid-fire but brief innings, ended almost as soon as Pakistan's captain Sarfaraz Ahmed brought back pace bowling to challenge him after he had blazed away early against the spinners.

"We showed some flexibility with our order. [Maxwell], his strike-rate was high but would like to see Maxi get a match-changing innings like he's done so many times before," Langer said. "We've got a very good batting side and I'm sure the opportunities will come. That's the beauty of having Glenn Maxwell in the team. He brings energy and we obviously know how brilliant he is against spin bowling, so that is the beauty of having him."

Australia's balance is also under question in terms of a fifth bowler, after Finch needed to share overs between Maxwell and himself in the absence of Stoinis or Mitchell Marsh. The former captain Allan Border has advocated making greater use of Smith's wrist spin, and Langer admitted it was highly unlikely he would be choosing a team with five specialists bowlers for the remainder of the tournament.

"We'll have to work it out, but it certainly makes it more problematic not having an allrounder in there," he said. "We've got a very, very strong batting side with the batting line-up we had I thought. It's probably harder for Finchy than anyone else to have less recognised bowlers I'll say, everyone's got to be on top of their game.

"You could [play five specialist bowlers], but it's very rare for an Australian team to do it. You see it in domestic cricket a bit, I think domestic cricket's a bit different than international cricket particularly with the wickets we play on, with the skill we play against. We could do it. We did it a few times last year when we were in England. You certainly can in T20 cricket. It's tougher in 50-over cricket but you never say never. We'll try and work out the best combination to beat Sri Lanka."

Nevertheless, Langer said that overall he was relieved to be sitting on three wins and one defeat ahead of Australia's meeting with Sri Lanka at The Oval. Victory there would further shore up a place in the top four, albeit with difficult fixtures against Bangladesh, England, New Zealand and South Africa still to come.

"I'm relieved. The best thing about it is we've got the points and we're nowhere near playing our best cricket yet." he said. "We've got four games in nine days or whatever and the boys are a bit weary already. We've got a really big game in the context of the competition at The Oval. But it's nice to have the points without playing our best cricket, so that's exciting."