De Boer, renowned as one of the best stoppers in the game, told his teammates on Thursday morning he wouldn't continue his career after 223 games for both the Giants and Fremantle.

The 32-year-old, who was a vital piece of GWS' grand final side in 2019, has played 12 games for the Giants this year.

De Boer was picked up by Fremantle in the 2009 rookie draft and played 138 games with the Dockers, before being taken with pick 56 in the 2016 draft and heading to the Giants.

Having built his game on effort - highlighted by two best clubman and a coaches' award - de Boer thanked his mentors for helping him produce his best football.

"I'd particularly like to thank (former GWS coach) Leon Cameron for believing in me and challenging me always to be the best version of myself," he said.

"I'd also like to thank the Fremantle Dockers for first recruiting me and, in particular, (former coaches) Mark Harvey and Ross Lyon for teaching me the abnormal effort and football IQ required to perform at the highest level.

"The Giants organisation and its people are truly a special place and have had a profound impact on not only me but my wife, family and friends.

"My heart is unequivocally full of gratitude and love for the friendships, memories and opportunities that playing in the AFL has availed me."

GWS football boss Jason McCartney called de Boer "the ultimate clubman".

"He's diligent and resilient and got the most out of himself as a footballer, while contributing enormously to team standards and culture," he said.

"Most AFL players never reach 200 AFL games and Matt's career is a testament to his hard work, sacrifice and relentless pursuit of excellence."

Australian Associated Press