Blues and North Harbour rugby player Michael Tamoaieta died suddenly on Friday.
The 23-year-old was a much-loved partner to Helen and father to daughter Aihara, and a dearly loved son and friend to many, the Blues said in a statement.
Tamoieta was a prop in the extended Blues squad and a former NZ Secondary Schools representative. He made 11 appearances for North Harbour in the Mitre 10 Cup.
Blues chief executive Michael Redman said they were stunned by the news and deeply saddened at his passing.
"Michael was a talented athlete, and our focus is to offer our support and sympathy for the family, and we are supporting our team and staff," said Redman.
NZ Rugby boss Steve Tew also offered his sympathies.
"Our sincerest condolences are with Michael's family at this very sad time," Tew said.
"Michael was a valued member of the Blues and North Harbour rugby environments and had been part of the New Zealand Secondary Schools team.
"We know his family, club and former school mates will be feeling this loss and our thoughts are with them all."
All Blacks forward Ardie Savea took to social media to pay tribute, tweeting "RIL uso" (Rest In Love).
The Blues also tweeted a message of support, stating "we love you Mikey T".
His family have asked for privacy, as they deal with the shock of his death.
The cause of death has not been made public.