Nico Rosberg has urged Mercedes not to get carried away despite his blistering pace on the final day in Bahrain.
Focusing on short qualifying runs in the morning's session, the 28-year-old crossed the line with a 1:33.283 to take the week's final P1.
It was an impressive lap as not only was it 1.6s up on second place Jenson Button but it also beat the week's previous best set by Lewis Hamilton by almost a full second.
Rosberg, though, says Mercedes need to remain cautious as lap times still don't count for much.
"In the morning I was doing some qualifying-style practices with lower fuel and that was good because I was feeling comfortable in the car," the German confirmed.
"I was able to push, we had a good balance and so I was pretty pleased with that. It's early days to say where we were because the other guys didn't take out as much fuel as we did, so we need to be very, very careful."
Rosberg, though, did encounter two issues on Saturday as he broke down out on track.
On the first occasion Mercedes said he stalled while practice starts while the team released no details on Rosberg's second red flag situation.
He continued: "For sure it's positive at the moment. In terms of reliability I managed to complete the race distance so that's been good.
"Nevertheless the car did break afterwards so there's still some way to go. So problems arising here and there, which is totally normal, and in comparison to other teams we are in a good position with reliability.
"But even us we need to be 100 per cent bullet proof by the time we get to Melbourne, which is a massive challenge and very, very difficult. So that's where the focus needs to be on."
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