Mercedes endured a tough day in Malaysia on Friday with Lewis Hamilton sixth and Valtteri Bottas seventh quickest behind the Ferraris, Red Bulls and the McLaren of Fernando Alonso, with Bottas admitting the team is lacking some performance around the Sepang circuit.
Hamilton was more than 1.4 seconds down on what championship rival Sebastian Vettel managed in second practice, via an off-track excursion through Turn 7.
The Briton says it is important Mercedes "regroups" overnight to ensure it doesn't struggle as much during qualifying.
"It’s been a very difficult day. I’ve been struggling with the car today, so we have to review and try to understand where we have gone wrong with the balancem" he said.
"We’re hoping that we’re able to find our bearings overnight and regroup for tomorrow."
Bottas meanwhile matched Hamilton's pace, and although various issues made the session a tricky one, he says Ferrari and Red Bull have the upperhand.
"Those were obviously tricky practice sessions," said the Finn. "We had quite limited running because of the rain in the morning. I also had a bit of an off in FP2 that cost us some time, we lost a few laps because of that. And then there was of course the red flag in the end.
"We didn’t get all the test items tested today, but I think that is going to be the case with all the teams.
"We’re definitely lacking some performance, it seems like Ferrari and Red Bull are very strong. So we have some work to do if we want to be on the front row tomorrow.
"The car balance itself didn’t feel too bad; it’s just a question of overall grip. The key area we are going to need to focus on tonight will be getting the maximum out of the tyres over one lap."
