Casey Stoner said he was not surprised that his illness continued to hamper him in free practice at Laguna Seca -- but did admit to some concern that it was an issue so early in the weekend.
The Ducati rider has hung on for third places in the last two grands prix despite struggling badly with stomach cramps and nausea. He was ill again by the end of Friday practice in America, having ended up third behind the Yamahas in the session after earlier holding a comfortable first place.
"I had plenty of time to recover between the Barcelona and Assen races but still encountered the same problems, so it's no surprise to come here after just six days and be struggling," said Stoner.
"The feeling of tiredness and sickness has started earlier than it did in those two race weekends so it's not looking good but again we have found a good setup with the bike, we know we have something competitive and I just wish I was able to use it more."
He hopes new treatments being tried this weekend might help to resolve the perplexing condition.
"It is hard for the doctors because I don't have any symptoms until I am physically tired, at which point I go rapidly down the other side of the hill, so it's not like they can give me antibiotics because they don't know what it is," Stoner said. "Anyway, they have given me something new to try here and we'll see if we can bring it back for race day. If it works I'll be very grateful."
The former champion added that he was confident he could take on the Yamahas at Laguna if his health allowed.
"Since Barcelona we've found a geometry set-up that gives me great feeling but I'm not getting the most out of it," he said. "I know it can go faster round here. We'll just have to see how the weekend pans out."