Mercedes W08 may have an engine reliability issue which the team purposefully concealed in Barcelona last week during pre-season testing.
The claim comes from well-known Italian insider Leo Turrini, a man close to Ferrari.
"It seems to me that in Barcelona the Mercedes had a reliability problem linked to the crankshaft," Turrini wrote on his blog.
"It's nothing serious, but Hamilton and Bottas were never able to push hard."
After two weeks in Barcelona and despite leaving Spain at the top of the timesheet, Ferrari still believes that Mercedes retains its advantage while the German outfit is underlining the Scuderia's impressive performance.
"It is certain that Mercedes will fix the problem before Melbourne, but Ferrari knows the story and that is why Ferrari believes the Silver Arrow is still ahead," Turrini added.
Only a proper race weekend will bring some clarity to the pecking order. We will get that next week, finally!