Blake played for the Hawke's Bay Sevens side during the summer and is displaying the benefits this season with superior fitness levels and work rates than in the past.
She agreed the Clive pack had more experience and size than Tech's but also pointed out with the likes of former Black Fern Amy Williams, player-coach Te Maari MacGregor, Karamu High School speedster Talon Robinson and in-form veteran Deidre Hakopa the riversiders' backline must not be underestimated either.
Like her sister, Blake has been reluctant to have any bets on the game.
"Regardless of the outcome I'm sure Nat and I will still have a good chat and laugh about the game ... we'll still love each other afterwards."
Cotton is confident Tech can gain revenge for their two losses to Clive earlier this season and retain the Marsh Cup.
"Last time we played Clive we weren't at full strength ... tomorrow night we will have most of our players available," Cotton said before joining her teammates for training at Whitmore Park last night.
Cotton, who captained the Hawke's Bay Tuis last year, pointed out she wasn't going to play this year but decided to have another season and help Tech out again. By that stage Blake had already decided to play for Clive.
"It was good playing alongside her for Tech and the Tuis last year but this year we've had to tackle each other a few times. Off the field we've got each other's backs but on the field our own teams come first," Cotton said.
The Havelock North ASB Bank branch manager, Cotton, said the sister rivalry didn't just happen on the field. They also competed against each other in the Hawke's Bay Rugby Union gym on Monday and Wednesday nights.
"Being a prop I beat her on the bench press."
"Yes. But I get her back come sprint time," Blake replied.
Their father, former Taradale and Clive premier halfback Ray Blake, is one of the more vocal supporters at women's rugby games, and Cotton predicted he will support Blake more tonight.
"But I will still hear him yelling out for me to get a bit lower at scrum time," Cotton added.
At the same time as the final Hastings Rugby and Sports will be playing Napier Pirate Rugby and Sports in the battle for third place on the adjacent field at Elwood Park.
Teams for the 6.30pm final
Clive: Holly Macdonald, Avelon Ropiha, Deidre Hakopa, Rebecca Mascall, Talon Robinson, Te Maari MacGregor, Lisa Ropiha, Jasmine Tihema, Laurae Blake, Jarnisae Whaitiri, Turu McIlroy, Yvonne Henare, Vicki Peni, Leanne Makea, Shantelle Moke. Substitutes: Sarah King, Niwa Johnson, Parker Montfort, Amy Williams, Kate Bradshaw.
Napier Technical: Aorere Piper, Nina Gill, Hine Kerrich, Chanel Huddleston, Davina Winiata, Tinesha Gill, Gemma Woods, Kate Brown, Tracy Whakaue-Smith, Cara Hall, Stacey Loye, Savali Apineru, Natalie Cotton, Forne Burkin, Rachel McKenzie. Substitutes: Cheyanne Aranui, Carol Baker, Turina Paku, Tiana Winiata, Sandy Tukaki.
