Fernando Alonso said a series of new parts on his Ferrari had delivered mixed results after going third quickest in Friday practice in Singapore.
The Spaniard ran with a new rear wing in the opening session but then reverted to an older design for the second session, when he posted his quickest time to end up behind Sebastian Vettel and Jenson Button on the times.
Speaking afterwards, Alonso said he felt it had been a positive day overall even if there was plenty of work still to be done – both on some of the new parts and on gaining a better understanding of the performance of the Pirelli tyres.
“We tried various new components on the car: some seem to be positive, others less so, but maybe in the case of the latter, we need to spend a bit more time for them to be developed as well as possible. Overall, I would say today was positive, even if the first impression is that we are not as competitive as we were in Monza, two weeks ago.
“We still lack a bit of performance on tracks like this one, where you need maximum aerodynamic downforce. From what we saw today, there's a significant difference between the two types of tyre, but we will have to wait until tomorrow to get a clear picture of the situation on this front. Maybe today's difference has been somewhat exaggerated by the evolution of the track surface. Testing the tyres over a long distance is very complicated on a track like this, because of the traffic, therefore it's difficult to make a direct comparison to our main competitors.
“I am reasonably sure that, on Sunday, we will see rather significant degradation and it will be important to manage that as well as possible.”
Team-mate Felipe Massa was ninth quickest in the second car but the Brazilian also felt there was work to be done to improve the performance of the car for race day.
"It wasn't an easy day for me,” he said. “The car wasn't right all day and I also suffered particularly badly with tyre degradation in both sessions. At the end of the second session, we found something that wasn't working properly, but that doesn't explain all my problems.
“We must find out what happened so we can fix it for the rest of the weekend. We have reasonably clear ideas about the direction to go in when it comes to set-up: one thing's certain, there's a lot of work to do."