Australia will narrow their list down to 15 names early next month but are able to make changes up to September 28, the day after the last of three ODIs in India and eight they will play in the lead-up to the World Cup.

"It is form based," chair of selectors George Bailey said about Labuschagne's omission. "We know Marnus at his best is good enough to hold down a spot in the one-day team, we just haven't seen enough of it consistently in the role that we'd like him to do. Leading into the World Cup, there's some opportunities for others to get a bit more game time.

"We've been really clear with Marnus, he's going to be part of some Australia A games around the same time so he can focus on some white-ball cricket. Clearly the squad we have going to South Africa have the frontrunning for [the World Cup] but Marnus, the age he is, the skillset he has, I have no doubt he'll play a part in one-day cricket in the future. We know at his best he can play a really important role in one-day cricket."

Australia A play New Zealand A in three one-dayers from September 10 to 15 in Mackay and Brisbane, the squad for which is due to be named this week. Shortly after that the domestic Marsh Cup begins which will give Labuschagne further opportunity to play one-day cricket for Queensland.

If, as expected, he now misses out on the World Cup it means he will be able to feature in a full run of Sheffield Shield matches during October and November ahead of the home Test season beginning against Pakistan, in Perth, on December 14.

Australia's Test players who feature in the World Cup will have very limited opportunity for any first-class cricket ahead of the Test summer, although it is unlikely any of them will be part of the five-match T20I series against India will follows the tournament.

The last round of Sheffield Shield matches before the Test series against Pakistan - and the BBL window - begins on November 28. The World Cup final takes place on November 19 and the round-robin matches finish on November 12.

"A really important thing to remember with Cam [is] he's doing his learning at the coalface in international cricket," Bailey said. "Even as far as Test cricket, he's going to play a huge role and be a really, really important member of that side and he's going to be a really important member of our white-ball teams in the near future. He's certainly one where it's about giving him a little bit more time off to make sure he hits the ground running for the one-day series."