Australian GP: Sebastian Vettel relieved at improved Red Bull

Sebastian Vettel admitted that it was "a big relief" to have a virtually trouble-free first practice day at the Australian Grand Prix.

The world champion's Red Bull team had a miserable pre-season but Vettel was fourth quickest at Albert Park, with team-mate Daniel Ricciardo sixth.

"A lot of work went into this. Neither of us had big problems and the balance felt very good," Vettel said.

"In terms of speed, we know there is a lot to come. So far it feels good."

Red Bull have come to Australia with a series of updates to the car to try to prevent the problems that had stopped them running in testing.

And while engine manufacturer Renault have admitted it is "not acceptable" to have come to the first race unprepared, it too has made progress.

Vettel said: "The biggest difference is we got new parts, not necessarily performance parts but we didn't have the spares at the testing and you end up with a fix here and there.

"Every lap right now is useful. It's a lot of new stuff for the whole team and myself, and we have to take each step and not rush into things. Today was a very good day.

"In a way it was a surprise because we didn't have any problems," Vettel said.

"The speed was all right - we didn't have a read on that during the winter, but it is only Friday.

"There are a lot of things you can play with in the car. How much power you run determines your lap time and your speed.

"We did our stuff to prepare as good as we can for tomorrow and Sunday, let's see where we are then. But so far so good."

Red Bull appear to be some way off the pace of the Mercedes team, who set a formidable standard on both one-off qualifying-style laps and longer runs with race levels of fuel.

But they appear to be probably the fastest of a group of teams behind Mercedes, which also includes Williams, McLaren and Ferrari.

Red Bull team principal Christian Horner said: "It's been a very strong first day for us. We've had a very difficult pre-season with numerous issues so it was refreshing to get some laps in and get a first proper feel for the car.

"We can see there is quite a gap to the Mercedes and the Ferrari but we are starting to feel what that gap is and by the end of the weekend we will have a clearer idea.

"It has been a challenging winter to design and then modify the RB10 but the team has responded to the challenge. There are always engineering solutions to engineering problems."

Full Australian Grand Prix second practice results

Details for BBC coverage of the 2014 F1 season