Johnson's roller coaster career was in limbo after he injured ligaments in his big left toe while batting in Australia's Test victory over South Africa last November and he missed the entire Australia season following surgery.
But the enigmatic 30-year-old fast bowler said he was already mentally shot by that point and in the doldrums over his cricket future.
"Going into that Test in Joburg, I was unsure if I could perform to be honest. It was at that point where I really just wanted to get away from the game and step back from it," Johnson said in Perth.
"The injury did come at the right time. I'd probably lost a bit of interest in playing the game.
"If I didn't get the injury, if I kept going, I could have got dropped and that could have been it.
"That (retirement) could have been on the cards for sure.
"I guess being away from the media helped a little bit, not copping it day in, day out. So that's been a bit of a relief."
Johnson, who has a reputation for erratic bowling, said he was confident his dark times were behind him, saying he felt mentally and physically stronger than at any previous point in his career.
The 47-Test veteran, with 190 wickets at 31.29, will have the chance to prove his worth in Australia's one-day tour of England in June-July.
He has also taken 168 wickets in 107 one-day internationals
