Anthony Foley's family say they've been "plunged into darkness" by the 42-year-old Munster head coach's sudden death.
Foley, one of Irish rugby's most popular figures, died at his team's hotel in Paris on Saturday night and their European Champions Cup match against Racing 92 scheduled for yesterday was postponed.
In a heartfelt statement Foley's family said, "Our anguish at the sudden loss of Anthony is bottomless."
Foley is survived by his wife and two children.
"We have been plunged deep into an incomprehensible darkness and sense of loss that we must work our way through over the coming days, weeks, months and years."
The family expressed their gratitude for hundreds of messages of sympathy from fans, many of whom signed books of condolences at Munster's Thomond Park ground and other centres in Limerick and across Munster.
"His sudden death has brought the rugby worlds of Shannon RFC, Munster, Ireland and much further afield crashing down," his family said.
"You have lost a former player, coach, friend and all-round inspiration - your and our hero both. We mourn his loss together."
Former Ireland coach Eddie O'Sullivan said Foley would have coached the national team one day.
"Leadership is a special skill. It's about knowing what to say and the time to say it. Anthony got that," he said.
Former Munster and Ireland team mate Ronan O'Gara tweeted: "Heartbroken, we have lost an incredible man."
Foley captained Munster to their first Heineken Cup final victory in 2006.
He won 62 caps for Ireland.