West Coast champion Josh Kennedy had just the right analogy to explain why his body was forcing him into retirement when mentally he still had the drive to keep playing. 

The fuel light is flashing red, Kennedy said, but he's still driving, trying to push through the final supply in his back-up tank before a final farewell against Adelaide at Optus Stadium on Sunday. 

Kennedy announced his retirement on Tuesday morning, delivering a speech to teammates that the star forward said he had rehearsed for about a year-and-a-half.  

The final decision to finish in what will be his 293rd AFL game coming because of a troublesome knee that he had pushed to its limits in his 17th season, against advice. 

"I've loved this game for so long, so there's probably a little bit left in the tank in terms of my headspace," Kennedy said on Tuesday.

"But body-wise it's probably sitting on that empty bit where your fuel gauge is flashing red, but you still drive a bit and you've probably got 30km left. 

"I'm pretty content with the decision based on the knee. 

"It's fine day to day, but it's probably just being able to compete and train constantly and get up week-to-week."

Kennedy spoke with coach Adam Simpson before the mid-season bye to confirm his decision to retire, later deciding on the Adelaide game as his farewell after reaching a goal of playing three games in a row. 

He said he had gone against the advice of Simpson and fitness and medical boss Warren Kofoed at stages this season to push through his knee issues. 

"The knee was giving me a bit of grief in pre-season, but I just wanted to train and play," he said. 

"[The recommendations] were that we just need to manage this, but I overruled and said I just want to play as much as I can and train as much as I can. 

"It was probably a bad decision, because that first half of the year was probably a bit tough on the knee. 

"The back end of the year we took Simmo's advice and have been able to manage and plan."

Kennedy, who will retire as the Eagles' leading goalkicker and one of the club's greatest contributors, was emotional on Tuesday when talking about the sacrifices made by his family, including wife Lauren and daughters Sage and Lottie.   

"As professional footballers and athletes, we become very selfish and it's 24/7 constantly thinking about your body and how to get better and how to get the best out of yourself," the dual Coleman medallist said. 

"We have so much focus on that, and with that you need balance. 

"The only way to get balance is for other people around you in your environment to be selfless. That's what my family has done ... I can't thank them enough."

Telling teammates was tough, Kennedy said, but he hoped he would be remembered as a player who had respect for those he ran out with. 

"I've never been that nervous," he said.  

"I told the boys that I've probably rehearsed that speech for about a year-and-a-half constantly on the way to trainings, to games, this morning, a few weeks ago. 

"Also at times when I thought I was going to retire a bit earlier than right now. 

"All I've ever wanted to be known for is having respect for my teammates and having my teammates say when they get asked the question about me is they wanted to play with me. 

"Any action or anything I've ever done on the field is trying to tailor towards having that respect from my teammates."

Kennedy said he would stay involved at West Coast any way he could, but life after football would involve helping run his labour hire business and contributing to Western Australia's mid-west where he hails from. 

"I've set up a foundation based in the mid-west called the Josh Kennedy Foundation," the 2018 premiership star said.  

"It's a bit of a passion project that will be based around helping disadvantaged youth in regional areas. 

"It's about helping facilitate and find what they want to aspire to and helping build an environment around them with resources to help them achieve their career goals."

A post-career appearance for Northampton could also be on the cards, honouring a promise to Geelong premiership defender Harry Taylor, with Kennedy also keen to play alongside Mark LeCras one more time. 

He expected Sunday's farewell to be emotional and surreal, saying goodbye to West Coast fans after what will be his 293rd AFL game and his 271st for the club, leaving him ranked outright fourth on the club's all-time games played list. 

"I'm not really fussed if I don't get a kick," he said.  

"I'm just glad to be out there and I'm going to relish every moment."