Waratah and Wallaby lock Alex Kanaar has been forced to retire after succumbing to a chronic knee injury.
Kanaar missed the entire season last year after undergoing an anterior cruciate ligament reconstruction on his left knee following an awkward fall during the Brumbies trial in January 2007.
"I really thought this was going to be a big year for me but my knee just wasn't responding to the level needed to play this game," said Kanaar.
"A few weeks ago I came to the realisation that my playing days were over and it was time to reassess my future.
"It was a tough period. I was really down and depressed but I came through it and now I'm positive about the future."
HSBC Waratahs Head Coach Ewen McKenzie said he was disappointed for Kanaar.
"The Waratahs have lost a significant player in Al and we're devastated as a team and upset for him personally," said McKenzie.
"He worked extremely hard to get back on the training paddock and this is something he doesn't deserve."
However Kanaar will not be completely lost to the Waratahs in 2008.
"I might not be playing but I still have commitments to NSW Rugby who have been extremely supportive through this whole process.
"I'm taking up a coaching position to help the Junior Waratahs and other development teams while continuing to assist in the promotion the Waratahs."
A well known advocate for the environment, Kanaar will continue to educate the Rugby community and others about climate change and sustainability.
"I'll be making the transition from Rugby life to a career based on my post-graduate studies in natural resource management," added Kanaar.
"It's something that's already having an impact with the Tahs. This includes an environmental day in partnership with the Australian Conservation Foundation and VISY."
In the meantime Kanaar will continue to undergo rehabilitation on his knee.
"Although I won't be able to play I do need to get my knee back to a state where I can function normally.
"The players have been great. They were shocked initially but understand the decision had to be made.
"I guess the good news is that I'm not walking out the door today. I'm a Waratah for life and my off-season has just begun."