The Brazilian's Williams team has performed well in pre-season and is currently comfortably ahead of Red Bull, but Massa expects a recovery.
Red Bull had one of its better pre-season test days in Bahrain on Friday, with Daniel Ricciardo setting the third fastest time of the day, and Massa has no doubts the reigning world champion team will recover.
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This is dependent on Renault continuing to make progress with its engines, which could also allow Lotus to climb the order.
"We saw that the Red Bull struggled every day, but the laptimes they did [on Friday] were not so bad," said Massa.
"You can't put Red Bull and Lotus on the side [as contenders] because when they fix the problems, we know that they have a good car and we know that they know how to make a winning car.
"It is always nice to say that a Red Bull is struggling and that maybe it can be fighting with the Caterhams, but forget it. It's not like that.
"They have a problem to solve, but when it is solved they will be there."
PLENTY TO DO FOR MASSA ON SATURDAY
Massa is completing his final day of running in Bahrain on Saturday and is hoping to gain more experience of the car to ensure Williams is in the best possible shape for the season-opening Australian Grand Prix on March 16.
As he completed only 65 laps during last week's first Bahrain test, Massa is keen to make the most of his two days of running in the final test.
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"There is still a lot to do and a lot to understand and I hope we can finish the day with more information about everything.
"[Friday] was actually my first day because I just did one afternoon last week and we know how important it is to drive, to understand.
"I'm happy with the way we are working, but still we need to understand the right direction, the right set-up, the right car to start in Australia.
"I hope we can have more working on the set-up to understand and be a little bit more prepared for Australia."
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