Sebastian Vettel and Mark Webber topped the timesheets, with Mercedes driver Nico Rosberg best of the rest, four tenths off the pace.
This is despite the best Red Bull lap during the eight days of testing at Barcelona being just over 2.3 seconds away from the best time.
Mercedes driver Lewis Hamilton has no doubts that Red Bull was sandbagging in testing.
"The Red Bull is massively quick as it always is, obviously they have been sandbagging the whole time in winter, as expected," said Hamilton.
"All of a sudden, they have pulled out a lot of time, but I don't feel we are miles away.
"To be able to say that we've gone from being really far away to not being too far away from Red Bull is pretty impressive."
Ferrari chief designer Nikolas Tombazis admitted that he expected to see the Red Bull RB9 setting the pace.
But he warned that it was too early to take the Friday times as indicative of the real pecking order.
"Red Bull showed to us they will be very competitive, which we never had any doubt about because they are a strong team and had a good performance in testing," said Tombazis.
"We don't know exactly what the relative pecking order is between the top four teams.
"Clearly, there are people who have made progress and people who have made a bit less progress.
"We need to wait for proper conditions to really judge where people are."
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