Though he feels Sauber has now fallen behind its key rivals in the development race now, Felipe Nasr says the team must not be tempted to rush through upgrades before they are ready.

The F1 rookie spearheaded a strong start to the year for the venerable Swiss team, consigning its dismal 2014 season to a distant memory with a top five finish in the very first race, before scoring again in China and Monaco.

However, while its mid-field rivals have brought updates to their packages in recent races, Nasr admits he is driving the same car he started the year with.

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An upgrade, complete with uprated Ferrari engine, is tipped to appear at the Belgian Grand Prix, but while Nasr admits he would like to get his hands on a more competitive car, at the same time he doesn't want it to be rushed.

"I am sure they working hard in the factory to have these numbers correct," he said. "For me I would prefer to wait for something that is going to fit properly, than to just throw things from race-t-race to see if it works. It is better to have something concrete that will work.

Indeed, though the engine upgrade is due for Spa, Nasr says he wants to see Sauber focus its efforts on aero development in order to improve the car's ability around high-speed corners.

"I just feel our car hasn't been updated at all," he said. "We have had minor updates on set-up and suspension, but the bigger lap time is to come on the aero side. The car becomes more stable, you are able to brake later, you carry more speed into the corners and you make your tyres work for longer.

"I am sure once you have this fundamental of the car working better, it improves the other areas. We need to have patience for the work on the key areas, but the main deficit of the car is the high-speed corners."