Mitch Marsh refused to reveal who Australia will pick to open alongside Travis Head on the eve of their one-day international series against England.
David Warner retired from the 50-over format after Australia's World Cup triumph in India last year, with Josh Inglis promoted to the top of the order in a 3-0 series victory against West Indies in February.
Jake Fraser-McGurk, who registered his maiden international fifty in the drawn T20 series against England last week, and stand-in captain Marsh are other alternatives for the vital role as Head's partner.
But Marsh, stepping up to deputise for Pat Cummins as skipper, gave nothing away when he faced the media ahead of Thursday's first ODI at Trent Bridge.
"We've got a few options. You'll have to find out at the toss, or when we bat," he told reporters on Wednesday.
Marsh hinted at fitness issues within the Australia camp as he said "we're still working through that but we'll have an XI on the park".
He did confirm that spinner Adam Zampa will play his 100th ODI in Nottingham.
Zampa was Australia's leading wicket-taker in their 2021 T20 World Cup and 2023 50-over World Cup successes and will likely be key as the tourists go in search of a 13th consecutive ODI victory.
"He's certainly tracking towards being one of our greatest ever ODI players," Marsh said.
"I feel very lucky to have him in this team. There's no hiding behind the fact he's certainly one of our go-to men with the ball.
"One of the challenges he's taken in his stride in the last few years is being that person for us and he certainly thrives off the bigger moments, which all great players do."