Daniel Ricciardo has admitted Red Bull are lagging behind Mercedes and Ferrari as pre-season testing draws to a close.

Despite widespread expectations that, with the introduction of more aerodynamic-friendly regulations, Red Bull would catch or even overtake Mercedes for the new F1 season, the RB13 has failed to impress in winter running at Barcelona.

Red Bull, along with sister outfit Toro Rosso and Renault, have been dogged by problems with Reanult's new power unit and Ricciardo lagged behind both Ferrari and Mercedes when the three teams attempted race simulations on the penultimate afternoon of the second and final test.

"I wish we were sandbagging a bit more," Ricciardo admitted to Sky Sports News HQ. "On Day One of this week's Test we looked more competitive. I would say that we're two or three tenths off the pace. Today was a lot more. Today we were not quick."

It is believed that Renault have assured all of their customer teams they will introduce a new engine for the season-opening Australian GP and Ricciardo remains hopeful Red Bull will be "pretty competitive" at the opening race.

The impression, however, is that Red Bull do not expect to match either Ferrari or Mercedes when the new season commences.

"Our true pace is closer but we are not quite at their level at the moment," said the Australian. "We can get there but we are not there yet."

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