Marshall in great form: Cayless

New Zealand captain Nathan Cayless says five-eighth Benji Marshall is in great form going into the Rugby League World Cup.

Marshall scored twice in the Kiwis 56 points to eight win against Tonga at the weekend.

New Zealand plays Australia at the Sydney Football Stadium on Sunday night after the official opening ceremony.

Cayless says Marshall was outstanding in a warm-up match against Tonga.

"(He) had some good touches, set up a couple of tries, scored a couple himself. He was very involved in the game," he said.

"He was running the football a lot, so that's great to see.

"Obviously he's got some of his confidence back ... not that he lacks much.

"But it's good. He's in our leadership group and taking a bit more responsibility on, so he's looking forward to this World Cup campaign."