The Fiat Yamaha star, who fractured a hand at the Valencian season finale earlier this month, has made the brave move from Michelin in an attempt to regain the world title he has lost for the past two seasons.

Rossi, who won the 2007 Spanish Grand Prix at Jerez on March 23 - and took victory in a rally car at Monza on Sunday - went on to finish his first day on the Japanese rubber with the third fastest lap time.

The Doctor circulated 0.293secs slower than Ducati's new world champion Casey Stoner, also on Bridgestone tyres, but comfortably inside his best Michelin race lap from the grand prix.

However, Rossi was only 0.296secs in front of the best Michelin-shod M1 of Colin Edwards, suggesting that the Italian didn't gain an instant grip advantage. Nevertheless, Rossi's 49 laps were enough to convince him that he'd made the correct decision.

"My first comment about the tyres is positive, and this has definitely been a positive day for us in terms of times and my feeling with the bike," declared Valentino. "My pace was not bad at all, even though my hand is still hurting, especially in braking. Let's say that I am at 90% fitness! I am happy with the choice I have made and I have great motivation for the task.

"Today it was also clear that there is a very high level of concentration from all the team members and this gives me even higher motivation, if possible. We have two more days, so it is not time for a final comment, but I am happy with the first day. Furthermore Furusawa-san is here, and this gives an idea of Yamaha's commitment to improve and to return to the top. Let's see how it goes tomorrow and let's hope it can be even better than it was today," he added.

"Today was the day we have all been waiting for," added team manager Davide Brivio. "It has been a very important day for us, because we've been looking forward to having the chance to confirm our decision. We also wanted to check Valentino's physical condition after the crash in Valencia. At the beginning of the test he suffered a bit, but he went better as the day went on, even if we know he is not at 100% yet.

"As far as the new work with Bridgestone is concerned, we made a good start," he confirmed. "Today we used all the time to get to know each other and to allow our engineers to interact with their technicians. We also worked to understand what kind of modifications we need to make to the bike, in order to make it work properly with the new tyres. Technically, of course, we have concentrated entirely on tyres and on understanding Valentino's initial comments about them. It was a good day with good times and we look forward to continuing the work tomorrow and on Thursday."

While Stoner set the pace with the new 2008 Ducati, Rossi, like all the Yamaha riders, is still testing with the 2007 spec machine. The 2008 M1 is due to make its debut at Sepang on January 22, after the winter test ban.