Nico Rosberg says challenge of 2012 Pirelli tyres is great for Formula 1

The closeness of the field this year has increased the influence of the Pirelli rubber on cars' overall performance. This has resulted in teams' form fluctuating as they work to get the rubber into the right operating window for their cars.

The four grands prix so far in 2012 have provided victories for McLaren, Ferrari, Mercedes and Red Bull, with no team having looked like repeating its success at any other circuit, such has been the vast difference in track conditions at each race.

When asked by AUTOSPORT whether races were becoming too much of a tyre-based lottery based on what has been seen so far this year, Mercedes driver Rosberg said: "No. It's just a very different game.

"We have seen already this year that when you go from one condition to another, one racetrack to another, one temperature to another... different cars are better on the tyres, so there's a very big engineering challenge to understand why, to adapt and to try and be the one to understand the tyres best. That can be a very big key for the season, so we're pushing hard to try and understand that quicker than others.

"Personally, I think it's great for the season. We've had four winners in four races, [so it is] all mixed up. It couldn't be better for Formula 1. Also within the races, with the tyre degradation and with lots of overtaking, we've had lots of exciting races."

Rosberg also claimed that the current performance window of the Mercedes, which was dominant in China and off the absolute frontrunning pace elsewhere, was not yet wide enough.

"Well we're not the best yet [in that regard], so of course we still need to improve in various areas," he added.

"I think we've progressed a lot recently; we were far off in the first race in Australia and even in the most difficult conditions in Bahrain we were there or thereabouts, beating, for example, McLaren and Ferrari. So we're looking much better, progressing in the right direction. We were the fastest car in China all weekend so we're moving forward very quickly."