World champion Vettel set the pace in both sessions on Friday, which included his fastest lap coming on the third lap of a run on the high-degradation supersoft tyre.
Webber made it a Red Bull one-two in the afternoon, but both drivers made it clear they were not getting carried away with the performance of the RB9.
"We are not getting fired up," Webber told reporters in the paddock. "We don't know what fuel loads people are running today.
"In general, not a bad start for us and we still have a bit of work to do."
When asked if Red Bull is the team to beat, Webber added: "We are not racing yet, so let's talk about it Sunday.
"We are going to have good chances in a lot of races. If this is another one, fantastic."
Vettel also tried not to draw too many conclusions from the first day of running, but he also hinted that there was still more to come from Red Bull.
"It was a good day considering it was the first day of the season," he said. "We can be very happy, and I think there is room for improvement."
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