Nico Rosberg has said that while Mercedes may be among the best in terms of reliability, the squad is still in a 'difficult position' and still struggling to make the car 100 percent bulletproof for the 2014 F1 season opener in Australia.

Rosberg concluded the second pre-season test by setting the best time of the week on Saturday, and while he also managed the most laps of any single driver over the four-days [see the combined times and laps - HERE], he remains cautious and is by no means getting carried away, even if the Brackley-based squad is looking very, very strong.

"It felt good and it has been a good day," he told reporters in Sakhir, including "We were doing lower fuel stuff in the morning and were really trying to get into the whole rhythm for qualifying - finding a balance for that. It was working well. I felt comfortable in the car and that is important to me, that I feel at home and everything is to my liking, all the set-up and everything. I got to grips with it well. I was really able to push it, which was nice - a good feeling."

"Then in the afternoon, we did a race simulation, which we managed to complete," he continued. "That is another big step for us. But of course afterwards the car broke. So there is still some way to go with regard to reliability.

"That [reliability] is very, very important. The early races are just going to be about reliability and who can get to the end. We are looking amongst the best in terms of reliability. But we are still in a difficult position."

Asked to summarise what he and Mercedes can take away from the second test, he added that outfit has learned a 'massive amount': "Every lap is important. Every lap you learn. We discovered a lot of reliability issues, which you only discover if you do many laps and really push the car to the limit. Those have been important discoveries," he explained.

"Now we have a couple of days to try and sort them out and hopefully we can reduce the amount of issues we are getting and by the time we get to Australia we will be able to finish the race."

So how happy is he and does he think he has a car that can really compete? "It is positive at the moment. In terms of reliability, as I said, I managed to complete the race distance and that has been good. Nevertheless the car did break afterwards and so there is still some way to go. But, problems arising here and there are pretty normal [at this stage]. I think in comparison to other teams we are in a good position, but even us, we need to be 100 percent bulletproof by the time we go 'down under'. That is a massive challenge and very, very difficult, but that is where the focus needs to be."

"I don't know yet [if we can challenge this season]. It is too early to say," he added. "It is impossible to know exactly what the other people were doing. There are so many different tyres here also. So, overall the feeling is positive. We are looking quite good, even on pace. But I don't want to say more than that because I just don't know."

Looking to the third and final pre-season test next week, which is also in Bahrain, he concluded: "The main focus still has to be reliability.

"There are four test days left [before round one] and still so many reliability problems out there, so that is the focus," he confirmed.