Sebastian Vettel admits it was a "big relief" to have such a productive day in Melbourne after Red Bull's difficult pre-season.
During the final outing in Bahrain, Vettel battled just to string a few laps together and on his penultimate day of testing did not complete even a single lap.
This prompted some concerns that Red Bull would struggle at the season-opening Australian GP.
And although Vettel's day got off to a sluggish start with just 10 laps in the opening practice, the reigning World Champion made up for that later in the day.
Covering 41 laps in FP2, he posted a 1:30.381 to finish fourth quickest on the soft Pirelli tyres. Vettel's time was 0.756s adrift of pace-setter Lewis Hamilton.
He said: "It was very good, it is a big relief, a lot of work went into this.
"Neither of us had big problems today, the cars were running and the balance felt very good.
"Times are not worth a lot at the end of Friday but it is better to be closer to the top rather than somewhere lost in the back.
"In terms of speed we know there is a lot more to come but so far it feels very good."
His team-mate Daniel Ricciardo finished the day sixth quickest with a 1:30.538 and 38 laps in the afternoon to go with his 26 from the earlier session.
Another person who was relieved was team boss Christian Horner.
He told the BBC: "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."
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