Heikki Kovalainen admits that his Lotus car's main problem is the lack of downforce, but the Finn is hopeful the team will be able to make progress with time.
After having to miss most of yesterday's testing session at Jerez following an accident early on, Kovalainen was able to complete nearly 70 laps today.
The Finn, however, was the slowest of all drivers, over four seconds off the pace set by Red Bull's Mark Webber.
The Lotus driver admitted the T127 is clearly lacking downforce, but he says it was only to be expected considering the team had to design and build the car in record time since gaining an entry for 2010.
"I think the main issue is the downforce," Kovalainen told reporters at the end of the day. "We have not been able to develop the aero package like we should do. We had five months to build the car and everything has been conservative. I mean, if you look at the car...
"Before they started to design the car they had no information about the engine, so cooling and everything is quite conservative. Sure we can improve. Just by looking at the car I could probably improve a few things. I'm sure we will be able to do this, but it will take a little bit time.
"Once we get everybody in the UK to start working, the design team and the manufacturing team, then we will be able to make big improvements, but I think it's quite clear that we are lacking downforce compared to the quickest cars. It's not surprising, we expected it. Just looking at the numbers we knew where we were going to be. "
Kovalainen is hopeful, however, that the improvements the team makes will be enough to take big steps forward.
"It feels like the improvements we are going to make will be quite significant," he said. "Sometimes in my previous team we were doing one and half tenths a race, or a tenth a race. It was quite difficult to feel it.
"Hopefully now we'll be able to make improvements that I can really feel, like the kind of step McLaren had last year in Hungary for me, when they really changed the car, and it was obvious that it was much better. I think we'll be able to do those.
"Also here we have a modified front wing compared to what we had at the launch, so I think we will be able to do something similar. Maybe not as frequently, as we don't have much research capacity to design and to look for things, but that's the way it is now."
Kovalainen's day was not trouble-free either on Friday, the Finn losing most of the morning due to problems with hydraulics and the clutch.
He was still satisfied with the work done after 68 laps.
"It was quite a long day for me, with all these laps adding up," said the Finn. "Yesterday unfortunately it was my error and today we had a hydraulic problem in the morning and a problem with the clutch.
"We lost the morning, but we got running in the afternoon, and we were able to do a few longer runs, so I managed to get a reasonable amount of laps, and we moved forward again.
"Of course I would like to do more running but I felt quite good today. It didn't take too long to get back the feeling and start pushing again."