The Silver Arrows have work to do overnight in Sepang, after ending Friday practice for the Malaysian Grand Prix in P6 and P7.
'It's been a very difficult day'
Lewis Hamilton could only manage sixth fastest on Friday, as he struggled for balance around the sweeping Sepang International Circuit, uncharacteristically spinning through the gravel at Turn 8.
Following the morning rain, practice two was completely dry, but Lewis ended the day 1.4s shy of Sebastian Vettel in the pacesetting Ferrari.
"It's been a very difficult day," said Lewis. "I've been struggling with the car today, so we have to review and try to understand where we have gone wrong with the balance. We're hoping that we're able to find our bearings overnight and regroup for tomorrow.
"I had a great group of people who were in front of my garage today all day long, sending really positive energy. So a big thank you to everyone there and I look forward to seeing you tomorrow!
'Those were obviously tricky practice sessions'
Valtteri was sixth, surviving his own hairy moment in FP2, skating through the gravel at the right-hander Turn 11 before returning to the pits.
"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 in 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."
'Overall it's been a very challenging day'
Trackside Engineering Director Andrew Shovlin conceded that the Silver Arrows will have to make strong gains overnight if they are to mix it with the Ferraris and Red Bulls in qualifying.
"Overall it's been a very challenging day," said Andrew. "The car wasn't working as well as it normally has done this year and the drivers were both complaining of very low grip and sliding.
"The car hasn't looked strong in any conditions, be it on Intermediates or in the dry conditions we had in FP2, so we're looking very carefully at the set-up and the configuration of the car just to try and understand what's gone wrong.
"We are clearly not getting the most out of the package here. We're going to be working very hard to unpick what we've seen today and come back stronger tomorrow. But at the moment it's clear we've got a lot of work to do if we're to present a good challenge to Ferrari and Red Bull this weekend."