For the first nine laps of Sunday's Grand Prix of Catalunya, Casey Stoner matched the Fiat Yamahas of Valentino Rossi and Jorge Lorenzo blow-for-blow at the front of the field.

Some changes to the set-up of the young Australian's Desmosedici had helped turn around a mixed Saturday, but the 2007 world champion's physical condition was heading dramatically downwards.

“On Saturday we really struggled with the bike, we were away too far off the pace to even be competitive. Then before the race we changed a few things and made a big improvement,” explained a visibly exhausted Stoner.

“I haven't felt in great shape all weekend – I wasn't ill but I wasn't quite myself. Then last night I couldn't sleep, I probably got a couple of hours at the most, and after just a couple of laps in warm-up I was destroyed," he revealed.

After setting the fastest lap of the race on lap 2, Stoner admitted he had nothing left by the halfway mark of the 25 laps, when he gave up on any chance of victory and began a damage limitation ride.

Despite his condition, Stoner was able to cling on to third position by just 0.052sec from Honda's Andrea Dovizioso, a result that means Stoner is now tied with Rossi and Lorenzo for the world championship lead.

"I was really afraid that I wouldn't finish the race. We did everything we could to prepare for it, but halfway through I gave up, I was absolutely dead and had nothing left.

“I started to suffer from really strong cramps and I could barely ride – I was falling over the front of the bike in the hard-braking areas and I was struggling to keep my concentration so I just decided to run around to get points.

“I was braking late to keep Andrea behind me and in the last two laps I put a bit more effort in.

“My bike was fantastic and if I wasn't so ill, I think I could have stayed with Valentino and Jorge until the end, although I'm not saying I could have beaten them," added the double 2009 race winner.