Boyd, 23, announced his bombshell decision on Thursday after negotiating a release with the Bulldogs.

"My decision to retire now is a reflection of issues I've had over the past five years, both with physical injury and with mental health," Boyd said via a Bulldogs statement.

"They have now accumulated to a point where I just don't have the desire to play or the enjoyment of the game I used to have.

"I am satisfied that this is the right decision for my future.

"I approached the club about my desire to retire and be released from my contract this week and we have worked out a mutually agreeable position."

That position means Boyd will forfeit more than two years of his multi-million dollar contract, agreed when he joined the Bulldogs from GWS Giants.

Boyd was signed by the Giants as the No.1 draft pick in 2013, and he played one season with the expansion side before heading back to his hometown in a blockbuster trade with the Bulldogs.

Boyd landed at Whitten Oval in exchange for current Bulldogs captain Ryan Griffen and the No.6 draft pick going to the Giants.

He signed a seven-year deal worth around one million dollars per year.

An accounting arrangement meant he was reported to have been paid around $1.7 million in 2016; which if true is likely to be the biggest single-season salary to an AFL player.

Given Boyd's status as an unproven teenager, the deal was considered high-risk for the club.

After brawling with teammate Zaine Cordy in mid-2016, the deal looked a lemon.

But it would pay off most handsomely in September, when Boyd starred in the Bulldogs team that roared through the finals series to win the club's first premiership in 62 years.

He was one of the best afield in the grand final win over Sydney, kicking three goals and taking six contested marks.

Boyd never reached those heights again.

In 2017, he took a prolonged leave as he dealt with clinical depression.

A back injury curtailed his 2018 season and he did not take the field in 2019.

Bulldogs football boss Chris Grant explained that Boyd had reached a point where he couldn't "get to the next level again to become an AFL player again".

Grant lamented but accepted Boyd's decision to leave the sport after 61 games and 50 goals.

"Everyone at the Bulldogs is saddened to hear of Tom's decision to retire, given he is a much-loved and respected person around the club," he said.

"Over the last few years we have worked very closely with Tom and his family to support him through a difficult period, and we will continue to offer that support as he enters the next phase of his life.

"We will not forget the role he played on the field, especially in the 2016 finals series when he showed the football world what he was capable of on the biggest stage possible."

Grant said Boyd never prioritised being financially compensated once he opted for retirement.

The mid-season retirement comes two months after fellow 2016 flag-winner Liam Picken decided to step away due to ongoing concussion issues.

It also allows the Bulldogs another pick in this month's mid-season rookie draft.

Australian Associated Press