MONTEREY, CA, JULY 23 - Fiat Yamaha's Valentino Rossi never thought it would be easy.Mazda Raceway Laguna Seca is the tightest and one of the most physically demanding circuits on the MotoGP calendar. With very few true straightaways and nowhere to rest, plus the plunging downhill Corkscrew, Rossi knew that it would be a severe test of the right leg he broke in his home race at Mugello the first weekend in June.The reigning world champion finished the first day of practice with the sixth fastest time and just under a second off pace-setter Casey Stoner and the Marlboro Ducati. And afterwards he admitted it had been a struggle."It is a bit bit more difficult at Laguna compared to Sachsenring, especially for my leg and also a little for my shoulder," he said. "What I am feeling is that the Corkscrew is a little more difficult physically to stop the bike, but especially when I go down to change direction and I have to push on the right leg I have some pain."Now I will put some ice and relax and hope that tomorrow it is not worse. At the same time I don't think we showed all our potential on the track, because we made a modification at the end of the session and I was able to do just two laps and then took the flag, so it would have been interesting if I had one or two extra laps. At the end I used the hard tire, but the hard tire today it was a little too hard, so maybe without he soft it was possible to go faster."A one-hour session was one thing. What about Sunday's 32-lap race?"Yes and now I have to understand how my body will react to the extra pain so the race will be hard with 32 laps, but I have to wait and tomorrow morning will be an important test also for the bike."Rossi was impressed by the speed of Stoner, whose Friday time of 1:21.699 was only slightly slower than his circuit record lap of 1:21.488 from 2008."The 21.6 by Stoner is a great lap time and he is already faster than the pole position of last year and this is a worry for everybody, a 21.6," he said incorrectly. Jorge Lorenzo's 2009 pole time was 1:21.678. "But the weekend is long and we try to recover."