Rugby league: Former Black Ferns Sevens star Niall Williams' warning to NZ Rugby after switching to rugby league

One of New Zealand's most high profile female rugby players has a message for officials after announcing she's switching codes.

Black Ferns sevens star Niall Williams has confirmed she's signed a one-year deal with Gold Coast Titans in the NRLW competition.

On her way out, she has a warning for NZ Rugby, as the battle to retain leading talent heats up.

After nearly a decade-long career for the Black Ferns Sevens, the Williams, 34, announced her retirement from the game earlier this year.

She will see out the world series circuit with New Zealand in France next month, before joining the NRLW competition in Australia for the next year and following in the footsteps of her brother, former All Black and Kiwis star Sonny Bill Williams, in making the code-swap.

Williams hasn't always envisaged a switch.

"I got a few offers about NRLW and that's when it kind of hit me - maybe," Williams told Newshub.

Because she's unlikely to be the last, she's imploring NZR to be more proactive around retaining its female players.

"I've just seen them sign [All Blacks and Blues star] Reiko Ioane for a few more years, so all we are asking for - if they're worth it - you're going to put the effort in to secure them for longer.

Longer is what Williams wants for women in New Zealand, with the NRLW providing the perfect alternative, if it doesn't happen.

"It's not saying, 'You know, I'm going to play NRL now, so you can't keep me'," she said. "It's just saying, 'If you value me and you want me to stick around, give me what I deserve and start pulling out those long term contracts'."

The code swap goes both ways. Former Kiwi Fern Katelyn Vaha'akolo has earned her first Black Ferns rugby contract, but it's only one of 34. 

She got a life-changing call from new Black Ferns director of rugby Allan Bunting.

"I low key thought I was in trouble, but when he offered [a contract] to me, I started crying," Vaha'akolo recalled.

There will be no tears for Williams, who will show others what is possible.

"Obviously, it's super exciting to see and she's paving the way for other people to come through," said Kiwi Ferns wing Madison Bartlett.

With an Olympics and Commonwealth Games on her CV, Williams could be back in black, but this time in a Kiwi Ferns jersey.

"If there was an opportunity and I earned it, I would definitely be pulling it on with a strong two hands," Williams insisted.

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