While the rest of the MotoGP field took to the wet Indianapolis track for Friday practice, world champion and 2009 title leader Valentino Rossi chose to save his engine for the first 20 minutes of the session.

New rules introduced last time at Brno limit each rider to a maximum of five engine changes during the final seven rounds, with a 10 point penalty should more be needed.

As such, and with the weather expected to improve as the weekend goes on, Rossi felt he had little to gain by putting unnecessary mileage on his Fiat Yamaha.

The Italian rode for 16 laps, the least of any rider except the injured Randy de Puniet, but still got within 0.152sec of fastest man Dani Pedrosa (Repsol Honda) on his last lap - and was just 0.003sec slower than Nicky Hayden (Ducati Marlboro).

"I sat out the first 20 minutes in order to save the engine mileage and by the time I went out it was very wet," said Rossi, winner of last year's storm-shortened Indy event. "Unfortunately the track wasn't draining so well where there is new asphalt and in some corners it was quite dangerous with standing water and a risk of aquaplaning.

"This weather was unlucky but it wasn't such a bad session and our pace and setting in the wet was quite good," he said of his third position. "We were able to improve the balance of the bike and if the conditions are like this again then we have some ideas to improve further. Luckily however it looks like the weather will be much better and so tomorrow we will start again from zero in the dry!"

Team-mate and nearest title rival Jorge Lorenzo - riding with a special 'Captain America' helmet, inspired by the famous comic-book hero - was just 0.08sec slower than Rossi for fourth position.

Lorenzo, who signed a new Yamaha contract earlier this week, took his first wet weather podium in last year's inaugural Indy event.

"This track has three kinds of asphalt and in some places the bikes looked like they were at sea!" said the Spaniard, who is 50 points behind Rossi. "The riding style was very complicated to get right today, above all in the first two sectors, but anyway I'm quite happy, especially because this is my first start after confirming that I'll stay with Yamaha next year and I'm proud to be here. I felt quite confident today even in the bad weather but hopefully tomorrow the sun will shine and we can see where we are in the dry."