Nico Rosberg says his leading time on the morning of day one of the second Formula 1 pre-season test was a result of Mercedes focusing on qualifying performance.
The world champion team did not use any tyres softer than the medium last week as it focused on gaining mileage and proving reliability.
But on Tuesday morning, Rosberg bolted on a set of soft tyres and set the pace with a 1m23.022s before handing the car to Lewis Hamilton for the afternoon.
"We were doing qualifying practice this morning," said Rosberg. "It's all the more enjoyable, to take the car to the limit.
"We did some fuel-light runs, which was nice for me to push some more.
"We got down to some decent laptimes. It was a good feeling."
Team-mate Hamilton completed a full race-simulation in the afternoon, starting on the softs before three further stints on the mediums.
Rosberg said he was pleased with Mercedes' programme so far in testing but insisted he was wary of the threat from Ferrari.
"It's been a good test," he said. "Reliability has been good and the speed has been there so it's all going to plan.
"But Ferrari has been close, they are a big threat.
"They have done a great job, but of course we are confident and we are ready for the battle."
Hamilton took 11 of the first 12 pole positions last year before Rosberg hit back in the closing stages with six successive poles to end the season.
When asked if qualifying will be key to him defeating Hamilton in the title fight, Rosberg said: "Not necessarily. But for sure I need to do well in qualifying.
"To beat Lewis, I have to do well in everything really - his level is very, very high."