The Black Ferns have opened their Pacific Four series campaign with a 23-10 victory over the Australian Wallaroos at a slippery, muddy Tauranga Domain.

It was a classic game of two halves, the Wallaroos dominant in the first stanza off the back of a powerful scrum, some tigerish breakdown work and a stack of errors by the new-look Black Ferns.

The second spell saw more energy from the home team, telling impact from the bench and far more accuracy and drive, while the Wallaroos were noticeably fatigued.

In the final analysis, the Black Ferns were the better team on a wet day, one for the forwards, scoring four tries to one and turning around their scrum issues to finish on top in the forward exchanges.

They also had, in No 8 Kaipo Olsen-Baker, just a month past her 20th birthday, the outstanding player on the day.

She scored a dynamic try, powering off the scrum and beating three on her charge to the line, while also effecting several crucial turnovers.

Australia seized the initiative early, scoring a try via loosehead prop Liz Patu, controlling the field position and possession, even winning a tighthead, while the Black Ferns were conceding penalties at a rate of two to one.

The one bright first half moment for the Black Ferns came when wing Ayesha Leti-I'iga crossed in the left corner, though she was taken in a high tackle by opposite Mahalia Murphy, who was lucky to avoid any sanction.

The nature of the match changed just minutes into the second half when the Black Ferns front-row subs entered the fray, debutante props Angel Mulu and Tanya Kalounivale putting the heat on in the scrums. Hazel Tubic used her nous and experience to good effect at five-eighths.

Kalounivale scored a try that was ruled out due to a rare, if technically correct, pre-latching call by the TMO. But the Black Ferns were undeterred, blindside flanker Alana Bremner scoring after a clever switch to the blind just moments later.

Olsen-Baker scored her try not long after that and the Black Ferns were now firmly in the ascendant. It came from a nice piece of deception by Kendra Cocksedge, who played with all her usual smarts and skill in her record 58th Test match. Her heads-up play led to Leti-I'iga's second try at the death, an overhead pass.

Of the other Black Ferns, debutante wing Ruby Tui ran with vigour and sought work, lock Maia Roos got stuck into her duties in the tight and made some gallops in the loose, while Alana Bremner and Leti-I'iga were both heavily involved.

Australia will feel disappointed that it could not keep the early pressure on, but the Wallaroos have proved they will be competitive for the August O'Reilly Cup series and the October 8 Rugby World Cup opener against the Black Ferns.

In the first match of the double-header, Canada scored six tries to one in a comfortable 36-5 victory over USA. The slippery conditions meant it was always going to be a forward battle, and the Canadian pack, led by captain and No 8 Sophie de Goede and lock Tyson Beukeboom, was just more efficient and accurate than the more limited Eagles.

This Sunday is the second Pac Four match day, at The Trusts Stadium, Waitakere. The USA Eagles will face the Wallaroos, before the Black Ferns lock horns with Canada.

Black Ferns 23 (Ayesha Leti-I'iga 2, Alana Bremner, Kaipo Olsen-Baker tries; Kendra Cocksedge pen) Australia 10 (Liz Patu try; Lori Cremer con, pen) HT: 10-5 Australia

-Campbell Burnes - allblacks.com