Sydney will lose immeasurable reserves of courage - and no little mysticism - at season's end after Brett Kirk elected to join coach Paul Roos in AFL retirement.

No-one has epitomised the unlikely marriage of Zen-like calm and old fashioned blood and guts that sums up the Swans teams of the past decade quite like Kirk.

And after playing 225 games with the Swans and leading the team to a premiership in 2005, Kirk announced on Wednesday this year would be his last.

Famed for his mental strength, 33-year-old Kirk said he had felt distracted and unable to focus in recent weeks.

"I know deep down this is the right time, I didn't want to keep fighting against it," Kirk told reporters on Wednesday.

"I fought against a lot, probably because of the way I got here, I tend to think I was up against a lot and that's probably what built me, built my character.

"I wasn't a great dad, I wasn't a great husband and I wasn't a great teammate or footballer last week.

"So I worked out that I needed to release this, I needed to tell someone.

"I want to be the dog that sticks its head out of the window and lets the wind fly through its hair, I want to enjoy the rest of the year."

Roos spoke of Kirk as a kindred spirit.

"Brett and I have similar philosophies in life," he said.

"Brett talked about some of the signs that led to the decision and I think life is a bit like that, some people are able to read the signs and some people tend to ignore the signs.

"He's aware enough to understand what life's about to throw at him and I think that resistance to those signs would have led to more stress and angst and all those sorts of things."

As well as changing the culture of the club, Kirk had influenced his coach too.

"Brett has been a very influential figure in this club and my life as well, so it's always emotional when those things happen," Roos said.

Kirk joined the Swans in 1998, but it was not until he reached the very edge of football oblivion in 2002 that he developed into the man who would be premiership co-captain in 2005.

A self-made player renowned for his workrate in the absence of any stand-out "weapon", Kirk has been widely admired as one of the best taggers in the game, also earning plaudits for his leadership at Sydney.

"I can't think of a player that's gone from a position that he was effectively staring down the barrel of having his career terminated ... to becoming an exceptional player and probably in the top five or six players of this club's history," said Roos.

"It would be a very different club if Kirky wasn't here."

The thought of Sydney without Kirk or Roos is difficult to contemplate, and the club has a sizeable task ahead to build again without the two men who have done so much to shape it.

For his part, Kirk has not thought much about the future, but it is hard to imagine the man who once sat at the Dalai Lama's feet taking up one of the usual post-football careers in coaching or punditry.

"I think if I start to think to much about what's next, I take my focus off what I'm doing now," he said.

"I'll wait and see which way the universe points and go with it."

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