Johnson will hang up his boots following the Bulldogs finals campaign, which the skipper hopes has three weeks remaining.
The Bulldogs face the Sydney Swans in a cut-throat final at the MCG this Saturday after being belted by Collingwood on the weekend.
Johnson, who has struggled with an achilles complaint for much of the year, was one of many Bulldogs who failed to have an impact.
But speaking from the Whitten Oval on Monday where he made his announcement at a packed auditorium, the 34-year-old said that performance alone had no bearing on his future.
“I’d made my decision quite a while ago that this would be it,” the 362-game veteran said.
“I played poorly on Saturday night ... my skill level dropped off.
“My last month of footy has been up and down. I didn’t play that well against the Cats (in round 20) and then played a quarter-and-a-half against the Swans and missed another week.
“So hopefully with that run under my belt [on Saturday night] I can bounce back.”
Johnson said battling injury this season had been a new experience for him, after going 16 years without any major ailments.
“Up until Christmas last year when I first felt my achilles I was going as well as I ever had,” he said.
“I’d come off a reasonable year last year and felt confident that I’d be able to have the same sort of impact this year but due to the achilles and a couple of other things along the way, that certainly hampered what I’ve been able to do in regards to preparing for games and obviously going into games.
“Every game though I’ve entered this year I’ve felt quite good and thought that I could have an impact.”
The goalkicker dismissed the idea of a well-timed announcement, designed to give his team a lift after its 10-goal loss to the Pies.
“I certainly didn’t want to use it as that sort of motivation,” he said.
“I get the opportunity to pull the jumper on, hopefully, three more times.
“We know what we’ve got to achieve and going into a final with this [announcement]... one thing we certainly don’t believe in is that false motivation.”
Johnson said he and his teammates still had the belief they could achieve great things this September.
That opinion differs to that of former Bulldog, Jason Akermanis, who has been critical not only of his former club but also Johnson since his sacking from the Whitten Oval.
Last month Akermanis called for Johnson to be dumped from Rodney Eade’s side, although the Bulldogs' skipper said those comments did not affect his self confidence.
“My focus and my beliefs are purely sitting behind you (his teammates), and that’s all I focus on,” Johnson said.
“I don’t get caught up in anything else that gets said on the outside of these walls.
“I rely on what the people in this room say and what the coaches have to say. I don’t have to answer to anyone else in regards to my footy or my employment at this footy club.”
