Nico Rosberg says he is concerned by the blistering that occurred on Pirelli's soft tyres during practice for the Brazilian Grand Prix.

Rosberg set the fastest time of both practice sessions at Interlagos, holding a 0.2s advantage over team-mate Lewis Hamilton. However, it was the longer runs that caught his attention, with the soft tyre suffering amid high track temperatures during the second session, and Rosberg hopes race day is cooler to ensure there is no repeat.

"It was just blistering, so they were starting to fall apart just because of the hot temperatures, which was very unusual," Rosberg said. "That was a bit worrying but probably we are expecting it to be not so hot on Sunday so it should be OK."

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Rosberg's pace was a result of some improvements to the balance of his car, as he said he was struggling with the front end early in FP1.

"It was a very normal day. The unusual thing though is that the asphalt is completely new on this track and it's very different to last year. It's much smoother, the asphalt, and that has a big impact on the car. So initially the balance was completely wrong, just massive understeer.

"So then we just had to adapt the setting and what you can do is you make the front end softer and the rear end much harder, that makes the rear work harder and then you have less understeer. So that's what we did a little bit and that worked out, I felt quite comfortable on one lap."

And Rosberg admitted he was surprised that there was so much grip available from a track surface that is less than a month old.

"It was a bit similar to Sochi, the asphalt here. It's very, very smooth, there's no holes. It's not very rough so you would think that there's less friction but somehow the tyres worked pretty well and there was extremely good grip today. That makes it nice to drive."