Casey Stoner had the bike but not the strength to challenge for a win at the Catalunya MotoGP where Valentino Rossi's victory turned the championship lead into a three-way tie.

Stoner, the 2007 world champion and the series leader going into the race, was third, eight seconds adrift, and later said he almost gave up due to severe stomach cramps and exhaustion, having had little sleep the night before.

"I probably got a couple of hours at the most and after just a couple of laps this morning (in the warm-up) I was destroyed," he said after Sunday's race.

"I was falling over the front of the bike in the hard-braking areas and I was struggling to keep my concentration.

"I thought about stopping but decided to just back off for a while and try to hang on for a top 10."

"I decided to race myself, basically, and bring home as many points as I could manage but my bike was fantastic and that is why I was able to ride it to a really valuable podium."

Stoner paid tribute to his team for supplying a perfect bike that enabled him to hold off Honda's Andrea Dovizioso, who finished a fraction of a second behind in fourth place.

"The team did a perfect job after the warm-up and if I wasn't so ill, I think I could have stayed with Valentino and Jorge (Lorenzo) until the end, although I'm not saying I could have beaten them," he said.

In what must have been one of the most exciting finishes to a senior Grand Prix, the lead changed three times on the final lap as Rossi battled with Yamaha team-mate Lorenzo.

The Italian displayed all the gifts that have brought him so much success over the years to get past on the final corner and claim his 99th victory in a major race.

"It was a great race and so exciting," Rossi said.

"It was so unbelievable and Jorge was so great."

Lorenzo, who has admitted that he is not the best of friends with Rossi off the track, added: "It was a memorable race.

"Valentino and me did our best to give a spectacle.

"We will see what happens in the next race," added the 22-year-old, who now shares the overall standings lead with Rossi and Stoner.

The three riders are locked on 106 points after six races.

Stoner's aim is to recover his strength for testing this week before beginning preparations for the Dutch round at Assen at the end of the month.

Fellow Aussie Chris Vermeulen finished the race in 11th place on his Suzuki, having been as low as 16th.

MONTMELO AFP/AAP