Australia captain Aaron Finch has little doubt Mitch Marsh would be ready to slot into the side if Marcus Stoinis' side strain leads to his withdrawal from their World Cup squad.

The injury Stoinis suffered in the loss against India last weekend led to the all-rounder missing out as Australia returned to winning ways against Pakistan and will also sideline him for Saturday's clash against Sri Lanka at the Oval.

His involvement for the rest of the tournament will be decided in the next few days but Marsh is on standby after linking up with the Australian party.

Finch, flanked by Australia fielding coach Brad Haddin's two young sons at his press conference, said: "(Stoinis) won't be available again. He hasn't bowled yet in his recovery over the last couple of days.

"So having four days between this game and the next game, I think that will be the ideal time to really test him out and assess him.

"But I think over the next five, six days there will be a call made on that, just based on what he can and can't do.

"We've seen him batting and running, no problem. Just he hasn't tried to bowl yet. Just waiting for the injury to settle down a bit more."

Marsh was due to travel with Australia's A side to England this week but flew over a couple of days earlier as cover for Stoinis.

Marsh has played no professional cricket since March while his last 50-over appearance was 18 months ago.

But if Cricket Australia does decide to trigger a formal request to remove Stoinis then Finch would back Marsh to be ready to face Bangladesh at Trent Bridge next Thursday.

Finch said: "The short answer is yes. There is confidence that Mitch will come in and do well if selected, if Stoinis doesn't recover properly."

The opener believes Australia, despite three wins from their opening four encounters, have yet to hit top gear in the tournament.

He said: "To come up against different opposition, you're facing different challenges all the time.

"I don't think we've gone anywhere near our best, which is still a good thing, that we've got six points on the board while not playing anywhere near our best cricket.

"But as long as we're improving, and continue to go up and not go backwards, I think that's the key. What per cent of 100 per cent game that you get to I think is irrelevant, as long as it's improving along the way."