Tandy believes Deaves will not be overawed by facing the All Blacks.
“It is on the biggest stage of all but I have every confidence in Harry,” said Tandy.
“He ain’t going to change but he will fit into what we are trying to do. I am excited to see him go.
“What a story to go up against the All Blacks, it’s going to be an amazing day for him, his family and the community.
“Whoever Harri plays on the weekend, it wouldn’t make a difference. He has got that freedom to go and attack the game. He loves being aggressive and competitive and has no fear.”
Deaves is following in an illustrious line of Ospreys open-side flankers who have graced the international game such as Tipuric, Marty Holah, Sam Underhill and Jac Morgan.
“We’ve been lucky with sevens at the Ospreys, there’s been a real conveyor belt over the years,” said Tipuric.
“I’m chuffed Deavsey has been recognised. He’s got this opportunity on the international stage to show everyone what he’s capable of.”
Pontyclun will be out in force to support their favourite son.
“It’s going to be an incredible day, one we’ll never forget,” said Probyn.
“I was never in doubt he would play for Wales. It was a matter of time but didn’t expect it to come this soon.
“There were tears in our eyes when he was announced in the team, so it will be overwhelming on Saturday.”
Whatever happens, Deaves aims to celebrate in his usual way.
“He’s told me he wants to be back in the club on Saturday night after the game,” said Probyn.
“He cannot wait to be back amongst his friends.”
Deaves and Pontyclun would not have it any other way.