Sergio Perez believes it is only a matter of time before Mercedes' engine rivals close the gap - and that they should do so before Australia.
Mercedes have had the better of the running in pre-season test, covering the most miles in Jerez and again this week in Bahrain.
Mercedes-powered teams have also set the pace with Force India quickest on Day One, McLaren on Day Two while Mercedes driver Lewis Hamilton posted the week's fastest time on Friday.
But despite having the edge in testing, Force India's Perez says Merc's rivals will catch up.
"I think the others will come back earlier than the first race," he told Autosport.
"The Mercedes is working fine, it seems reliable. But things are going to change.
"I'm sure we will see the other manufacturers come back and it will be a very close battle between the front and the midfield."
Perez, though, says it has not been all smooth sailing as demonstrated by his delayed start on Friday morning.
The Mexican racer was not able to leave the pits for the first two hours as his Force India team worked on his VJM07.
"The other teams are having issues, but everyone is at the moment.
"Even us, this morning we had a big delay of two hours so we didn't manage to complete the full programme.
"Other teams are struggling in the same way, so it's difficult."
He added: "I wouldn't draw that conclusion yet.
"We are definitely doing good work before Melbourne, which is the target. We will see what we can do before the first race."
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