A LETTER from an 11-year-old Western Bulldogs fan pleading for Zak Butters to join the Dogs can be revealed as an unlikely key moment in the superstar free agent's decision to join his boyhood club.

AFL.com.au revealed on Saturday morning that Butters had nominated the Western Bulldogs as his preferred new home, having agonised between the Bulldogs and Geelong as his choice after departing Port Adelaide.

And more light can be shed on the decision that saw Butters ultimately move away from choosing the Cats to land on the Bulldogs, including a letter that was hand-delivered to his letterbox in western Victoria last week.

In the letter, signed by 11-year-old Hunter, the Dogs supporter pleaded with Butters to follow his heart and choose the Bulldogs, with a 20-cent piece also stuck to the handwritten letter.

The letter struck a chord with Butters who, amid the Bulldogs' record $2 million a season offer over nine years, had started by then to lean back towards the Western Bulldogs, who he supported as a kid and recognised the impact he would have on the next wave of western suburbs kids following the club.

Over the following days, Butters formally decided to choose the Bulldogs, informing them on Friday of his call after they had spent more than 18 months wooing him back to the western district in the biggest rival coup in the club's history. 

It is a scene inspired by the events of 1996, when a six-year-old Bulldogs fan named Ryan Adams mailed Chris Grant a heartfelt letter with a 20-cent coin attached, asking the Dogs hero to keep it if he stayed with the club as he weighed and then knocked back an enormous offer to join Port Adelaide ahead of its inaugural season.

And it has had the same impact, with the move resonating with Butters as he grappled with the emotions of his decision.

The letter to the three-time best and fairest winner and three-time All-Australian midfielder reads:

"Zak, I heard that you are leaving Port. Your childhood team needs you Zak. Can you please come to the Doggies? And since your parents live in Bacchus Marsh it's quicker to drive to Mars Stadium than GMHBA Stadium. And the Dogs have a really good midfield and with you we will be unstoppable and win multiple flags.

"If you can play for the Dogs it will leave a lifetime of happy memories, please go to the Dogs. It would mean a lot to me. Here is 20 cents of my money it's not much and it's all I have but giving my savings to you will be worth it if you play for the Dogs.

"Please Zak come to the Dogs. From Hunter, 11 years old."

The Bulldogs pulled on the heartstrings of Butters to make his call but have also been workshopping different trade scenarios with the Power about how a deal could get done between the clubs.

AFL.com.au revealed earlier this month that Butters leaving as a free agent and netting the Power pick No.5 as part of a wider suite of moves that includes other trades between the clubs had been part of discussions.

The AFL has been aware and taken through the options by both clubs, but the League has also written to clubs about all trades needing to stand on their merits.