Adam Cooney was convinced to join Essendon rather than North Melbourne because of his relationship with James Hird and his desire to play under the returning Dons coach.   

Cooney became a Bomber on Thursday after the Western Bulldogs agreed to trade him in the dying hours of the NAB AFL Trade Period.

The deal was done in the dying hours of the NAB AFL Trade Period and only became possible after Essendon finalised its drawn-out negotiations with Port Adelaide over Patrick Ryder by acceptin picks No. 17 and No. 37 in exchange for the disgruntled ruckman.

The Bombers passed on pick No.37 to the Bulldogs for the 29-year-old Cooney, who will depart the Whitten Oval after 219 games in 11 seasons.

Essendon pipped North Melbourne in the race to sign Cooney, with North having offered the Bulldogs Kieran Harper and a swap of its pick No.36 for the Dogs' pick No.45.

Essendon list manager Adrian Dodoro said it was Hird, who is due to return as Essendon coach in 2015 after serving a 12-month ban, who convinced Cooney to choose the Dons.

"They really hit it off and he wanted to play for him," Dodoro said as the Bombers left Etihad Stadium on Thursday.

"It was his relationship with James Hird.

"Our indoor facility was something Adam was really impressed with because of the sponginess of the floor."

Cooney has inked a two-year deal with the Dons and list manager Adrian Dodoro said the club was delighted to secure Cooney's signature.

"We are very excited Adam has chosen to join our club and look forward to the experience he adds to our playing group," Dodoro said.

"Adam will add important outside speed to our side and is a proven performer which is evident through his 2008 Brownlow Medal."

Cooney told the Bulldogs at the start of the trade period that he was open to a move after his relationship with coach Brendan McCartney deteriorated in 2014.

It was speculated that McCartney's departure last Friday might convince Cooney to stay, but ultimately the utility has decided he needs a fresh start.

Cooney joins Ryan Griffen and Shaun Higgins in exiting Whitten Oval with Jason Tutt and Liam Jones also set to depart.

The No.1 pick in the 2003 NAB AFL Draft, Cooney won the 2008 Brownlow Medal and that same year was named an All Australian and finished second in the Bulldogs' best and fairest award.

Unfortunately, he cracked his right patella in the 2008 finals series and has had to manage his knee ever since.

Cooney's knee degenerated to the extent that he played just 27 games in 2011 and 2012, when he was a shadow of his former self.

But at the end of 2012 he received cutting-edge treatment in Germany that has helped him turn his career around.

The treatment involved taking blood from his arm, separating and incubating its growth cells and injecting them into his knee. 

It helped Cooney train harder than he had in years and return to close to his best form.

In 2013, he finished seventh in the Bulldogs' best and fairest award, having averaged 25.5 possessions and one goal in his 19 games.

Cooney was not as consistent this year, but still averaged nearly 20 possessions in 18 games.