Jack Watts during Port Adelaide's official team photo shoot at Alberton Oval in February, 2020. Picture: AFL Photos

JACK Watts has announced his immediate retirement, bringing an end to a much-scrutinised career firstly at Melbourne then at Port Adelaide.

Watts had a season to run on the four-year deal he signed with the Power in the 2017 AFL Trade Period, but the mental and physical toll of a serious leg injury last year led him to this decision.

The 29-year-old was the No.1 draft pick in 2008 and played 174 games in total, but only two since the end of the 2018 season and none post-injury.

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"I have been thinking long and hard about my future for a while and contemplating retirement," Watts said.

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"Since my injury, I feel my body has let me down and I have been struggling with the physical and mental requirements of getting back to the level of fitness that's required at AFL level. 

>> WATCH THE INCIDENT IN THE PLAYER BELOW

"Speaking with Ken (Hinkley) and Chris (Davies) and my manager in the last few weeks, it feels like the right decision for me to step away and look for new challenges in the next phase of my life. 

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"I feel lucky to have had 12 years in the game and while there have been some challenges, there have also been some amazing memories both at Melbourne and Port Adelaide."

Watts was a lightning rod for criticism from the start, with the Demons' decision to select him for his senior debut in the 2009 Queen's Birthday game against Collingwood haunting him forever.

The Magpies physically targeted the then-lightly framed teenager and Melbourne was amid one of the least successful eras in club history.

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Watts, who was selected ahead of All-Australian ruckman Nic Naitanui in his draft year, became a good player for the Demons without ever reaching the heights expected of him.

His best year was in 2016, when he kicked a career-most 38 goals and finished fifth in the club's best and fairest award – but he came 21st in the same count a season later that preceded his trade.

Jack Watts, Steele Sidebottom and Nic Naitanui at the 2008 NAB AFL Draft Camp. Picture: AFL Photos

Watts made 19 appearances for Port Adelaide in his first season there, but found trouble at the start of the 2019 season, when a video of him snorting a legal substance off a woman's chest circulated on social media.

Power president David Koch slammed the incident as "the height of stupidity" and "simply brainless".