Richie Mo'unga booted a last-minute penalty to lift New Zealand to a 23-20 comeback win over a much-improved Australia in the second Bledisloe Cup match in Dunedin on Saturday.

Richie Mo'unga booted a last-minute penalty to lift New Zealand to a 23-20 comeback win over a much-improved Australia in the second Bledisloe Cup match in Dunedin on Saturday.

Debut tries from winger Shaun Stevenson and backrower Samipeni Finau helped the All Blacks rally from 17-3 down at half-time when it looked like their 22-year home win streak against the Wallabies was in peril.

Ardie Savea sparked the All Blacks' rally with a try-saving tackle in the first half and proved a force at the break-down throughout the contest.

The win is New Zealand's fourth in succession this year and ensured they swept the two-Test Bledisloe Cup series against their Antipodean neighbours. However, head coach Ian Foster's decision to field a second-string starting side nearly blew up in his face.