Australia's 24-22 victory over New Zealand came despite the Kiwis dominating territory; two of the Kangaroos' five tries came from interceptions, and two more followed kicks.
New Zealand could not turn that advantage into a win, leaving coach Stacey Jones frustrated. "Unfortunately, we were on the losing side, but we will learn from it and we will get better, and we will make some adjustments," he said.
Kalyn Ponga scored twice in his long-awaited debut for the Kiwis but left late with a suspected broken arm, putting his Rugby League World Cup campaign in doubt.
The Newcastle captain had played through pain for the final 20 minutes before Keano Kini replaced him. Jones said: "He couldn't catch a ball or anything like that. He was in a bit of discomfort."
Ponga, cleared earlier this year to represent New Zealand, will have scans and further assessment on Friday before the team returns home.
"He's going to go and get the scans done and we'll see where it goes from there," Jones said. "He's obviously disappointed, but there's a bit of upbeat about him too. He really wants to still be involved."
If Ponga is ruled out, New Zealand can seek approval to add a player to its squad. Jones said Kini would likely take his place against the Cook Islands in Christchurch next week.
The Kiwis then face Fiji in their final group match. They are seeking their first World Cup title since 2008, and captain James Fisher-Harris said: "I thought he did an outstanding job, he's a freakish player, but he's also one of those tough players. We're feeling for him right now, but fingers crossed it's not too bad."