Reigning MotoGP world champion Casey Stoner may have crashed out of the last two races, effectively ending his 2008 title hopes, but the Ducati Marlboro rider believes points lost during the early part of the season were just as costly.

Despite winning the Qatar season opener, Stoner struggled at the following four rounds - netting just 31 out of a possible 100 points - before finishing on the podium at the next six events, three of which he won.

That podium run concluded with a second position behind Valentino Rossi at Laguna Seca, a stand-out race in which the world championship leader frustrated Stoner into a small mistake.

Casey remounted to finish second, but has fallen whilst pushing to stay ahead of Rossi at the two rounds since, leaving the young Australian 75 points behind with just five rounds and 125 points up for grabs.

"It was gone awhile ago, and we started to bring it back and it was gone again," said Casey of the 2008 world championship. "We always kept things reasonably open, but we were also just trying each race by race, just trying to do what we could. You know, not so much for the championship, but just the races themselves.

"I think the championship, like I said, was gone quite a few times. We gave too many points away at the beginning of the season, and that's really stung us now. So we, you know, with these two crashes, I think if we hadn't done such a bad beginning of the season, we would have still been within reach, but that's the way things have gone this year.

"We're not putting the blame on anybody and I've been riding the best I can," Stoner continued. "The practice sessions have gone perfectly, and I've been learning a lot more. But, yeah, I mean, the races just haven't worked out. I felt that I was doing everything right like I have in the past and, you know, they really caught me out, these two crashes.

"So I'm a little bit disappointed with my results in the last few races. I'm here learning, I'm young, and we'll see how it goes at this racetrack."

Stoner is now just two points ahead of Repsol Honda's Dani Pedrosa heading into this weekend's inaugural Indianapolis Grand Prix, and will be riding with a broken scaphoid bone in his left wrist.

"I never actually re-broke it; it never healed in five years," he said of the injury. "I've been a little disappointed with the news of that. I thought it was sorted five years ago, but I kept having quite a lot of pains over the years, every now and then, nothing bad enough; and they just kept telling me, 'It's fine, it's fine, scaphoids do this,' but we've had X-rays and scans and realise that the bone basically broke itself into a few pieces. We have got to decide what to do in the future with it, but for now we have just got to keep racing and see what we can do."

Nevertheless, Stoner is excited by MotoGP's new Indy adventure.

"Yeah, I mean, we haven't even been able to [learn the track layout] with the PlayStation or anything, unless we went backwards on the Formula One game, which I don't think you can do!" he joked.

"It's definitely going to be a very new track. When we came to Laguna, we knew which way it went, and when we went to Turkey, we knew which way it went. Here is a little different.

"You know, it's going to be exciting getting out there tomorrow morning."