Lewis Hamilton admitted that he was not content with his McLaren's performance in free practice in Singapore, although he is optimistic that he can get the car on the pace in time for qualifying.
The world champion was only seventh and ninth in today's two sessions.
"I'm still lacking some speed in certain areas, so I need to work on that," said Hamilton. "The sessions were a little up and down for me today - I didn't have any major problems, but I wasn't as fast as I'd hoped to be.
"Today's not the important day though, and when the track gets a bit cleaner tomorrow, we'll have a better understanding of the tyres. The main thing for us is to analyse the data, try and improve the car and find some more time for tomorrow."
But his team-mate Heikki Kovalainen was much more upbeat having been third in second practice.
"I'm very happy," said the Finn. "I didn't have any problems today and I think we made some good progress between the sessions. Both tyre compounds seem to work okay, so that's another reason to be optimistic.
"I'm confident we can find a bit more time overnight, too. However, the other teams are also looking quick here, so it's not going to be easy."
Team boss Martin Whitmarsh reckons McLaren is in reasonable shape, but that the race might see a return to the days of Brawn fighting against Red Bull for victory.
"While we don't appear to be the only team suffering from oversteer issues today, it certainly looks like the cars setting the benchmark here are the Brawns and the Red Bulls," he said.