For the second time this season, circumstances beyond Valentino Rossi's control ended his chances of a podium finish - and dealt his championship hopes a further blow.

The Italian's Spanish Grand Prix chances effectively ended when he was hit from behind at turn one, but no other rider was involved in his costly retirement from Sunday's Chinese Grand Prix - a front tyre failure ending the world champion's charge from 13th on the grid.

Rossi's climb up the order was unexpectedly slow during the opening laps - the Italian rising to tenth at the end of lap one, but then staying there for the next three laps. The reason was that he was stuck behind a certain Marco Melandri during that time and wasn't impressed with some of his countryman's "strong" moves.

"I didn't get a bad start to the race and I passed a lot of riders but I had a battle with Marco Melandri that cost me some time. Some of his moves were quite strong, which I could understand if we were fighting for the win on the last lap but not for ninth place at that stage of the race," said Valentino.

After finally passing the Fortuna Honda rider, Rossi made good progress - passing Loris Capirossi, Shinya Nakano, Casey Stoner and Sete Gibernau to hold fifth place by lap 9 of 22. With Repsol Honda riders Dani Pedrosa and Nicky Hayden soon pulling away up front, victory looked out of the question - but the third placed battle between team-mate Colin Edwards and Suzuki's John Hopkins was well within touch, the pair being just three-seconds ahead.

Unlike team-mate Edwards, who only set the eighth fastest race lap due to chatter, Rossi was able to extract much more speed from his M1 - allowing him to catch Edwards and Hopkins on lap 14, when he also set the third fastest lap of the race. But disaster struck soon after when a chunk of rubber was thrown from his front tyre, destroying the front fender and leaving the Doctor with a severe vibration.

It now appears that Rossi rode another lap with his bike in that condition, but was losing touch with Edwards and Hopkins - and soon looking at the rear of his machine. The Italian correctly guessed that he had a severe tyre problem, but wrongly thought it was the rear which had failed (as is normally the case).

The #46 pulled into the pits for a tyre change on lap 16, pointing at his rear wheel as he drew to a halt. Camel Yamaha duly changed the rear and, in the heat of the moment, apparently didn't spot the missing front fender and damage to the front tyre - although Rossi's friend Uccio began frantically pointing at the front of the bike just as he pulled away. Valentino himself soon realised the error and rode slowly around the lap before retiring.

"The bike felt good but just as I got my pace to 2min 0.1secs it suddenly started to feel wrong and I thought I had a problem with the rear tyre," conformed Rossi. "I came in to change it but as I went back out I realised it was actually the front tyre, so that was the end of the race for me.