Former Australia lock Dan Vickerman has died aged 37, former club Waratahs have announced.
The former Brumbies and Waratahs player, who made 63 appearances for Australia, died at his family home in Sydney and is survived by wife Sarah and two sons.
The South Africa-born forward, who spent a season in the Aviva Premiership side Northampton, retired from the game in 2012, with his last international appearance coming in the semi-final of the 2011 Rugby World Cup.
After retirement he worked for the Rugby Union Players' Association.
RUPA chief executive Ross Xenos said in a statement that appeared on Waratahs' official website: "On behalf of all players, we extend our deepest sympathies to Dan's young family at this difficult time. We are truly shocked and united in our despair.
"Dan was universally respected by his peers and the rugby community during and beyond his playing days. Since retiring, he was very generous in giving back to the game through coaching and voluntary roles supporting players' off-field development."
Waratahs CEO Andrew Hore said: "His tireless commitment and passion to helping improve rugby, as well as his commitment to supporting players throughout their careers through his role with RUPA, is a legacy that will long live on.
"The shockwaves of his tragic passing will be felt right across our rugby community. Our thoughts are with his wife Sarah, their two sons and other friends and family during this difficult time."
Vickerman could have made more appearances for the Wallabies had he not taken a three-year break from international commitments while he studied at Cambridge University, where he competed in two varsity matches against Oxford.
In a statement, former international team-mate Phil Waugh said: "We're all devastated about our good friend and team-mate, Vicks. I think I speak on behalf of all players in saying that our thoughts and prayers are with his wife Sarah and the boys.
"Out of respect to them, we'd prefer not to say too much more except that we are thinking of them and his family at this difficult time and he will always be in our hearts."
Another ex-team-mate Quade Cooper wrote on Twitter: "Shocked an old team mate Dan Vickerman has passed away..Grateful to have played along side you..Thoughts & prayers are with his wife & 2kids".
Tributes came from all corners, with a tweet from the New Zealand team's account reading: "The #AllBlacks join the rugby family in mourning the passing of former Wallabies lock Dan Vickerman. Rest in Peace."
Incredibly saddened waking up to the news of Dan Vickerman. A true gentleman of the game. Thoughts are with his family.
Rest easy Vicks— Adam Ashley-Cooper (@AdamCoopy) February 19, 2017