Reece Walsh scored once and helped create five tries as Australia beat Cook Islands 66-6 in Townsville on Saturday night.
Despite Walsh's man-of-the-match display, coach Kevin Walters said he had not settled the team's spine for Sunday's World Cup semi-final at Allianz Stadium.
"I haven't decided. I keep telling everyone but you seem to think that I am a bullshitter and I am lying to you," Walters said.
"I haven't made any decisions around who is playing where."
Half Tom Dearden, who recorded two try assists against the Cook Islands, was preferred to Sam Walker.
Walters said Dearden had not simply taken Walker's place, and both had met the team's standards.
"Both players have performed really well and to high standards that we believe they can play to. It is another decision we will have to make in the next couple of days."
Walsh had ice on his left ankle after the match, but Walters described him as "fine" and did not guarantee his selection.
James Tedesco and Walker had played in Australia's 36-22 win over Fiji the previous week, and Walters said Tedesco had also performed strongly.
"He set up four tries last week. We are just fortunate with some of the players that we have in the group that selections are tough. It is a good position to be in as a coach."
Walters said Australia's defence and collective mentality had improved against the Cook Islands.
"When we can defend well we have a lot of belief in the attack that we can score points."