Just when MotoGP rookie Jorge Lorenzo looked to have put a spate of accidents behind him, the Spaniard suffered a huge highside on the very first lap of the US Grand Prix at Laguna Seca, ending his American debut in the Turn Five gravel.

Lorenzo made a good start and was up to fourth place when the accident, similar in magnitude to his Shanghai fall, happened. It was immediately clear that the Estoril winner had injured himself, a depressing realisation for a rider who has already had to cope with two broken ankles (Shanghai) and a concussion (Catalunya) this season.

It was later confirmed that the 21-year-old Fiat Yamaha rider broke the third and fifth metatarsal bones in his left foot and - while he at least has the summer break to recuperate - still faces a race against time to be fully fit for the Czech Republic Grand Prix on August 17.

"I'm very sad today because I had a lot of confidence for the race after the qualifying session yesterday and, above all, after the very start of the race when I was fourth and feeling good," said Lorenzo, who flow home on Sunday night for further assessment in Barcelona this week. "Then I crashed; my tyre was not up to temperature, I lost the rear and the next thing I knew I was in the gravel, with pain in my foot.

"It is one more crash, one more injury and it's another moment that I have to forget as soon as possible. I need to look forward. I am so sad but now I must concentrate on the fact that I have a whole month before Brno in order to be fit and to be able to race in good shape. This is my aim," he added.

"The main problem today was the lack of grip on the rear, which was amplified at the beginning of the race when the tyres were not yet at the optimum temperature," confirmed team manager Daniele Romagnoli. "Now let's hope for a good rest for Jorge; we wish him a good recovery and we look forward to seeing him come back at Brno ready to fight again with the top riders."

Meanwhile, there was at least cause for celebration the other side of the factory Yamaha garage as team-mate Valentino Rossi took his first ever US Grand Prix victory, following a scintillating battle with Casey Stoner.

"I would like to congratulate to Valentino for his great victory and race today, he did a fantastic job," said Lorenzo.