Johnson posted another impressive performance against the Melbourne Renegades on Friday night, recording 3-13 to capture the Player of the Match gong.
The proven performer has clearly found his bowling style across a long and successful career, but has drawn discussions comparing his blistering pace to the variations of other bowlers such as teammate Andrew Tye.
Johnson said the slower ball was definitely in his repertoire, but captain Adam Voges had made it pretty clear it was to be used sparingly.
"I try it (slower ball) every now and then, but the last game Vogesy got up me for it," Johnson said.
"He said, 'What are you doing bowling slower balls? That's the last time you bowl slower balls at the WACA.'
"And it's probably a fair point, especially when it was going through pretty nicely.
"It was pretty dumb on my behalf.
"I don't mind bowling slower balls and I bowled a few here (at Etihad) ... it just depends on the batter and how you're feeling, how the game feels.
"You've got to be unpredictable as a bowler - when you become predictable, it's an easier game (for the batters)."