Former Manly premiership winner Darrel Williams has put nationality ahead of club allegiance and is tipping the New Zealand Warriors to upset the Sea Eagles in Saturday's NRL preliminary final.

The 1987 grand final winner with Manly is a former Kiwi centre and current Test selector and believes the Warriors can carry their hot form all the way to the grand final.

But his tip comes with one proviso.

"If this is being read in New Zealand, then yes," he quipped.

Seriously though, Williams is confident of a Warriors upset at the Sydney Football Stadium after their back-to-back wins over Melbourne and Sydney Roosters.

"Absolutely. The Warriors are showing things they haven't shown for a while, that's a new grit and discipline. They're on a roll and every team in the competition is taking notice," Williams said.

"They're playing with good confidence and showed some really good signs coming back in the second half (against the Roosters on Friday).

"That wasn't typical of them in the past, so it looks like they've got some new resolve which is a real positive.

"Their wins from eighth place gave them a huge self-belief. No team's done that before so it was a huge psychological barrier winning that game (against Melbourne).

"The Sea Eagles are in for a really tough night and it's up to them to come and get the Warriors, I reckon."

But Williams couldn't help but put a foot in each camp, adding he thought the Sea Eagles deserved to be premiership favourites.

"Manly are very solid and they've shown less chinks in their armour than Melbourne," he said.

"They're probably the most solid side in the comp without being the flashiest.

"But if their forwards are held by the Warriors forwards then they're in for a real battle."

Williams will do it tough in the grandstand on Saturday, 21 years after his side beat Canberra 18-8 in the decider.

He'll be there as Kiwis selector with an eye to next month's World Cup, but his Manly connections remain strong.

He still lives on the northern beaches, managed Manly's iconic Steyne Hotel for eight years, and shares a traditional pre-grand final beer there with his old Mt Albert clubmates each year.

He's also organising a reunion of former Manly first graders for Friday next week, so a Sea Eagles win on Saturday would be ideal.

"They'll all come out of the woodwork, about 100-150 of them. (Former teammate) Cliffy Lyons rang yesterday and he wants 1000 tickets for Saturday - I don't know where he expects me to get them from," Williams said.

"My heart still lies in New Zealand. I live in Australia and I'm still very much involved with the Manly club, but I'll always be a Kiwi."

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