They once butted heads during one of the fiercest rivalries played out in modern football, now they’ve joined forces to guide the Sydney Swans into a new era.

Ten years ago, if you had of told Brett Kirk and Tadhg Kennelly they’d one day be calling the shots in the same coaches’ box as Dean Cox they all would have scoffed at such a bold prediction.

In fact, “I would have thought you were crazy,” Cox laughed.

But the fact is the wheels are well and truly in motion, and the Sydney Swans are already calling Cox, the most dominant and revered ruckman at the height of the rivalry, one of their own.

A six-time All Australian and (dare we say it) premiership star, Cox spent the past 18 years with West Coast, first as a towering ruckman of 290 games, then as an assistant coach under Adam Simpson.

While it pained him to leave the Eagles after so many years of service, Cox described how a new environment was critical for his development and was stretched thinking of a better organisation to continue his football career with.

“Once I was done with playing, if I was to go somewhere else, the Swans have always been one of the top clubs I wanted to get to,” Cox explained.

“When you first get drafted, you don’t know where you’re going. But as a coach, you have a bit more of a say and you get to work in an environment you think will enhance your coaching career and pass on what you’ve learnt as a player and coach.

“Being an organisation that’s been successful for a long time, there’s a lot that the football club does really well and that I can learn from.”

Cox spent his first few weeks doing just that, learning and absorbing new philosophies, discovering what makes his new club tick and mapping out the way forward alongside the rest of the new-look coaching panel which has included Steve Johnson coming on board, Kirk's move to the midfield group, Kennelly's return, Laidler's transition into coaching and Shaw's senior promotion.

After long days in match committee, his first day on the track was warmly welcomed as the second-to-fourth-year players returned for their first pre-season session.

Cox joined his fellow assistants in the middle of Weigall Oval in Darlinghurst under grey skies, looking on as the players literally hit the ground running. Eager to get involved, the 204cm big man jumped in on several drills throughout the morning, providing quite the obstacle for George Hewett, Ollie Florent and Will Hayward to dodge.

At the height of the rivalry, Cox spent many of his 20 games against the Sydney Swans seeing red while focusing on keeping the footy out of the eager arms of the likes of Kirk, Jude Bolton and Ryan O’Keefe.

On that drizzly November 13 morning, Cox found himself wearing red (and white) while swapping war stories and cracking jokes with the old enemy.

“It’s amazing how things change,” he said, as Kirk studiously studied training vision in the neighbouring office.

“One thing Brett always did was get the best out of himself. He was team-orientated and did whatever he could to get the result for the football club, which was something I always admired from the other side of the country.

“I get to build a relationship now, work closely with him and pick his brains along with the other guys. I’m really looking forward to a long career coaching with him.”

The rivalry between Cox’s Eagles and Kennelly's and Kirk’s Swans was as fierce as the fanfare and headlines – underpinned by the match score lines of the time.

The boiling point came between 2005 and 2007 when six consecutive games were decided by less than five points; two were grand finals of the highest quality, the spoils of which were split down the middle when the clashes cooled to a simmer.

“As much as it would have been nice to win both,” Cox said of ‘05 and ’06 grand finals, “it was probably fitting that we got one each.”

Cox added, in jest: "I probably wouldn't have been allowed in the building had we won both."

The Swans and Eagles always had a mutual respect but once the players from each camp crossed that white line, Cox says, with a wry smile, “she was on!”

West Coast also always knew what to expect from Paul Roos’ men, and vice-versa, an understanding which helped build and strengthen a rivalry that led to many magical moments.

Now Cox, Kirk and Kennelly are now all retired – Cox being the last to hang up the boots in 2014 – that respect for one another has grown.

Even more so now that they’ll be rubbing shoulders and working towards continued success at the Sydney Swans.