To the neutral observer, the defining moment of the 2005 AFL Grand Final was Leo Barry's mark.

Even diehard West Coast fans would think Barry's pluck, to deny the Eagles one last surge at victory, was THE moment of that epic encounter. Some commentators called it the mark of century.

That view is not universal. And it most definitely is not mine, but my vision has long been jaundiced by the blue and gold dye running through my eyeballs.

To be fair, it is a view very much in the minority. If more people had my insight into the events of that amazing match, perhaps there would be more than a handful who would support me on this one.

I was working on the interchange bench that day, trying to keep tabs on 42 players with a magnetic board, arranging and re-arranging match-ups as players exited and entered the arena.

It was a tough, mentally challenging gig and required absolute attention. Really, it was a futile exercise, but it was seen at the time to be of some importance.

Amid the helter-skelter of players coming and going - and the high anxiety of the pressurised atmosphere on the bench - there was a point in the first quarter when those levels were accelerated well above the norm.

Our physio had been on the ground assessing an ankle injury suffered by Daniel Kerr, about mid-term. He came back to report to the coaches box that it was not good.

Typically, Kerr tried to push through, but after a few minutes he had to concede, came off and received medical attention.

After assessment and treatment he trotted along the boundary line.

“Good to go,” he said.

No one was convinced.

But this was a grand final. And this was Daniel Kerr.

He did return and he played out the game in typically brave fashion. But his impact was undoubtedly diminished, and West Coast missed his verve and class around the ball. That was the critical factor in the game. The margin was a paltry four points and Kerr was worth so much more than that!

Barry's classic climb, as good as it was, would not have been even slightly significant had Kerr been able to play at anywhere near his best.

The little maestro, in conjunction with Ben Cousins and Chris Judd, formed an elite midfield. As good as there has ever been in the game.

Had Kerr won Brownlow and Norm Smith Medals - as he could so easily have done - then perhaps he would be lauded the equal of his high calibre teammates. Certainly, he deserves to stand alongside them, though he cannot compare medals. 

This week, the club and Kerr reached agreement with the AFL on the terms under which the champion on-baller could retire. Given he had a contract for 2014, it's now not as simple as deciding the time has arrived and agreeing to the financial terms before bidding adieu, cleaning out your locker and heading off into the future.

Kerr told his teammates six weeks ago that his body could no longer stand the rigours of AFL footy. His diminutive frame had copped a hammering through 220 games and it simply could withstand that punishment any more.

It doesn't matter how tough an individual might be, there comes a time when the body cannot respond to the mind's questions.

And kilo for kilo, there has been no one tougher than Kerr in this game in the last 13 years.

Selected at pick 18 in the 2000 draft, he showed as early as the pre-season matches leading into his first season that he was a special talent.

His appetite for the contest was unquenchable. An instinctive ball player, he hunted the footy and in an intra-club practice match, I remember thinking the club had selected astutely.

Over the course of the next 13 seasons, there was no reason to re-evaluate.

To get a sense of that fine competitive attribute, called 'mongrel' in the football vernacular, you just need to understand Kerr's pedigree. His father, Roger, was a feisty midfielder of some achievement with East Fremantle and Port Adelaide, while his mother, Roxanne, is genetically aligned to the Regan clan. A Fremantle family renowned as tough, uncompromising and gifted.

Daniel displayed those traits in equal measure.

As it is with the game's finest players, there are moments in their careers which stand to define them.

In the instance of this pocket dynamo, one came in a derby against Fremantle in 2003 when he gathered the ball in the back half of the ground, bounced his way (left-handed bounces of course) through the midfield, cut through the 50-metre arc and then, despite his exhausted state, summoned the required energy to convert the opportunity. It won the AFL goal of the year.

That left-handed bounce was one of his signatures. Purists - and junior coaches would say - that right-footers should bounce with the right hand in the interests of balance, poise and delivery. But Kerr was never one for convention.

The other enduring memory came in the round one match against Sydney in 2007 at Telstra Stadium, the Olympic venue.

As the competition heavy weights, who had squared off in the previous two spine-tingling grand finals, continued an amazing sequence of tight finishes, they prepared for a fresh start. But this would be a replica of the recent matches.

West Coast, however, went into the game without about 30 per cent of its premiership team.

In the dying moments, Sydney star Jarrad McVeigh took possession just inside the Swans’ attacking 50, with his team trailing by a point. He had time and space - or at least he thought he did - before Kerr sprang out of the darkness, like a cougar, and latched onto his prey.

McVeigh was caught holding the footy, West Coast gained possession and with no further score won, another outstanding match in an amazing sequence of contests was decided by less than a goal.

Great players so often impose themselves at clutch moments and Kerr made a habit of doing so.

Less specific memories revolve around his relationship with Dean Cox, another of those champions of this era who will forever hold a special place in the history of our club.

So many times Cox would deftly place the ball into the path of the rampaging Kerr, who would receive it at top speed and then deliver precisely further afield.

But there was one other innate ability that truly set him apart.

In the congestion in the midfield, which generally saw the superstars assembled, Kerr had a vision like no other. A Picasso, among Michelangelos, if you like. An abstract mind opposed to genius.

Not only could he envisage the play before taking possession, he had the capacity to execute it in the most pressurised of times.

His left hand as lethal as any weapon in the game, he could hit a running target on the outside of the skirmish with remarkable precision. The skill of an expert marksman, he could thread a bullet-like handball to a player the opposition might have considered surplus to the stoppage.

Of course Kerr was not perfect. He had his moments off-field, but he should be judged on what he did for this footy club. And while many stand physically taller, metaphorically, he has been a pillar.   

It will be a long time before we see another of his kind. If, indeed, we are again fortunate enough to witness such a phenomenon.