Mercedes admits it has found itself "quite a way behind" and with work to do over the next two days to recover from an assortment of issues that dogged its opening day of testing in Bahrain.
The reigning world champions were hit with trouble at the outset of the session when Valtteri Bottas suffered a transmission problem on the W12's installation lap that required a gearbox change.
The team was hoping for a trouble-free afternoon and although Lewis Hamilton managed 42 laps, the Briton was left stranded in the Mercedes garage for a lengthy period as his crews dealt with a balance issue.
"It's been a poor start to the season from us today," acknowledged Mercedes trackside engineering director Andrew Shovlin.
"We lost more or less the whole morning with Valtteri with a gearbox problem and our workload over lunch meant we were late joining the afternoon session with Lewis.
"Once we got running it was clear we didn't have the car in the right balance window and while we made some progress during the day, we're not happy with how the car is performing and it's pretty clear we have some work to do.
"We're quite a way behind on our test programme and need to find a bit of balance and speed but we have two days left and every opportunity to recover the situation."
©Mercedes
Hamilton vowed to remain positive amid the setbacks and the misfortune, and rely on his experience moving froward.
"These things are sent to try us," Hamilton said. "Everyone has worked extremely hard to get us here.
"We had that mishap in the morning which was very unfortunate for Valtteri in terms of losing time on track and the team is working hard to try and understand what that was.
"We have no choice but to take the positives. I remember in 2007 during testing I had 10 days in the car and now it's getting less and less.
"We only have a day and a half in the car before the first race, with different tyres and different aero modifications so it's not easy but it's the same for everyone.
"I'd like to think my nine years' experience with this team will help me get the best out of it."
In the challenging afternoon session, the Briton was seen battling his car more than usual as he struggled with Bahrain's low-grip and sandy conditions.
"I've never seen a sandstorm come through here before in all the years that I've driven at this circuit," Hamilton said.
"The sand was moving like rain would move. Having sand on the tyres isn't good for their longevity and getting consistency on long runs is difficult.
"Over a single lap it isn't the worst, but you need lots of laps at this time of year to get data."
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