Aussie rider Casey Stoner was far from impressed with his fourth placing at the US Grand Prix.  He confesses he is still making a great physical effort to overcome an unknown illness.

Stoner also follows another body wrenching weekend.  While he was courageous enough to place fourth, the 2007 champion lost precious ground on champion Valentino Rossi, who finished behind winner Dani Pedrosa at Laguna Seca.

Rossi now gains a nine-point lead over Jorge Lorenzo, Stoner is an additional seven points back in third place.

The 23-year-old explains his physical health was improved the past two races, however he is still reaching for 100 percent physicality.  "It has been a weekend to forget. I can't be happy with fourth place even if it has limited the damage to my championship chances," he states. "Today I didn't feel as bad at the end of the race as I have done in the last two but I'm still not right. I found it really difficult to keep my concentration over the last few laps and I was in a bit of a daze by the end." "My left arm was feeling really tired by the end because of the fact there are so many left-handers here and my left wrist still doesn't have the full range of movement after my operation in the winter."

Stoner will stay in the US for further medical tests at the Fremont Surgery Centre to grasp the source of the issue, before starting to prepare for the next round of the season in Germany on Sunday July 19.

"Now we'll focus on trying to find out the root of the problem because racing in this condition is not much fun," he explains.