Felipe Nasr says he is impressed with his first impressions of the Sauber C35 as the Swiss team gave the car its belated track debut at the second pre-season F1 test in Spain.

With late changes to the F1 calendar putting Sauber on the back foot in preparing new Ferrari-powered car, it was forced to run last year's C34 at the first test as it put finishing touches to the C35.

Nonetheless, the car enjoyed a successful first run out in the hands of Nasr, completing 103 laps out of the box and experiencing only minor teething issues.

Indeed, despite the late introduction, the Brazilian was impressed with what he found as a first effort, saying the car has improved in key areas, such as rear stability and braking.

"It was good to clocked that many laps in our first day with the car was quite impressive," he said. "We normally expect to have more things to fix but it was quite a smooth day. In the morning there was some tuning on the system side, but nothing major really.

"There is still a lot of work to do, I am sure we will see a progression of the car over the few days. The first impression was good, it felt like a step forward from last year, from the chassis and the engine/gearbox side.

"As a back to back from the car to last week we seem to have a more a stable rear, when looking at medium and high speed corners."