"The intensity and length of the BBL is just too much for someone who will be 37 at the start of the summer," Johnson's manager, Sam Halvorsen, told The West Australian newspaper.
"Mitch has put his name up for the Emirates tournament in Dubai, but that is half the length of the BBL."
Cricket Australia on Wednesday announced an expanded season for the next edition of the BBL, starting in December. The final will be played in February. There will be 59 matches played in total, with each side playing each other twice (home and away) during the regular season. Each team will play 14 matches before the final stage of the tournament begins.
The season will also see BBL matches being played at the Metricon Stadium in Gold Coast for the first time, just a month after the venue plays host to its first international T20 between Australia and South Africa.
Johnson had been on a year-by-year contract with the Scorchers. Shane Watson, Chris Lynn, James Faulkner and Ben Laughlin have already been selected in this week's "mini-draft" in Dubai for the T10 tournament and the fast bowler is among the pool of players for the main draft on September 2.
First Published: July 25, 2018, 8:39 AM IST