Adrian Sutil admitted that Sauber still needs to work on some of the aerodynamic aspects of the C33 car, but added that he is happy with Ferrari's new power unit.
During the Jerez test last week, Sauber used a launch specification aero package on the car but will upgrade that with a an "extensive package" in Bahrain in a fortnight's time during the second official pre-season Test.
"The conditions were just not so good and we were struggling mostly to keep the tyres up to temperature. So we were struggling to do a longer run - longer than five laps - because we lost so much temperature that it was almost undriveable. So the runs were quite short but we covered over 60 laps [on the final day] so that's not too bad," Sutil said.
"We need to put some downforce on the car and make it driveable. I think this is the most important thing.
"All the brake systems and engine-wise I think we're quite comfortable with the Ferrari package - they did a good job - so we have to focus on our car, driveability and especially the aerodynamics."