Wainui has died in a car crash near Tauranga on Monday morning.
The crash happened just before 8am at McLaren Falls Park, with the 25-year-old dying at the scene as the sole occupant of the vehicle.
Chiefs and Māori All Blacks coach Clayton McMillan said Wainui's death was a huge loss.
"Sean was an incredibly talented individual and held a great amount of mana among his fellow teammates and the wider rugby community.