Fiji may field an under-strength side for Sunday's Rugby World Cup match against Australia to save its best players for the following game against Wales.

The Pacific Islanders are currently level with Australia on 10 points at the top of Pool B after defeating Japan and Canada and coach Ilie Tabua says their best chance of advancing to the quarter-finals will come from beating Wales.

"Knowing that our following match is a three-day turnaround, we need certain players rested and we need to vary it around knowing that Australia would have looked at all our games so far and assessed all our players," Tabua told reporters on Tuesday.

"It doesn't mean we will not put out a good team. We may have a different nucleus to what we have had in the past two matches but we will put out a side with a mix of both senior players and younger players."

Tabua, a former Wallaby and Fijian international, admitted there was an obvious danger with focusing everything Wales to sacrifice the match against Australia.

"We don't want to look past Australia -- first things first," he said. "People are talking about Wales, but no, we have a game at hand and this is a game that counts first, then Wales."

Fiji captain Mosese Rauluni said his team had not written off an upset win over the Wallabies despite the possibility of fielding a weakened lineup.

"Everyone is talking about Wales but if we can knock Australia off it makes it a lot easier for us in the pool," he said. "Whatever team we pick, it's a squad of 30, those boys are just as capable as us.

"I know the young boys are raring to go, they haven't had a run yet and if they do get a chance I know they will do their best for Fiji.