Casey Stoner's hopes of retaining his MotoGP world title suffered a devastating blow at Brno on Sunday, when the Australian crashed out of a one-second lead over Valentino Rossi - gifting the Italian his fifth victory of the season and doubling his title lead to 50 points over the Ducati rider.

After their epic Laguna Seca battle, which finally went in Rossi's favour after Stoner stumbled under braking, Brno was always going to be a crucial event - and the two title contenders were in a class of their own all weekend.

Stoner led four of the five track sessions heading into the race, where he converted pole position into an early lead, whilst Rossi looked in trouble after losing second place to John Hopkins.

But while Stoner set a scorching pace to try and crush the opposition, Rossi kept his victory hopes alive by passing Hopkins and then matching Stoner blow-for-blow over the following laps - pushing the pair over ten-seconds clear of third position by lap five!

Stoner's lead over Rossi sat at a stationary 1.2secs until lap six, when the Fiat Yamaha star pulled two tenths back from the #1. Perhaps attempting to respond, Stoner lost the front of his Desmosedici through a right-hand turn on the next lap, sending him sliding into the gravel.

The triple 2008 race winner sprang to his feet and attempted to rejoin, but the damage to his Desmosedici was too great and Casey was forced to accept a second non-score of the year (after a mechanical problem in France) at arguably the worst moment possible.

Rossi was never troubled thereafter, stretching his advantage to an enormous 15 seconds at the chequered flag - while an entertaining scrap for the remaining podium places kept the fans entertained.

After Stoner's fall, Rizla Suzuki riders Chris Vermeulen and Loris Capirossi were promoted to second and third positions, with Hopkins holding fourth for Kawasaki and Toni Elias - who lined-up just 13th on the grid - fifth ahead of Anthony West.

Capirossi briefly took second position from his team-mate, but Elias - who has a habit of producing career saving rides, perfectly illustrated by his shock victory in the 2006 Portuguese Grand Prix - threw his Alice Ducati past Hopkins, Capirossi and Vermeulen in one lap to claim second position on lap 10 of 22.

Whilst continuing to lose ground to an out-of-sight Rossi, Elias was able to safely confirm his first Desmosedici podium by six seconds from Capirossi, who marked his record-equally 276th grand prix start with a debut Suzuki rostrum.

Hopkins, making his return from a three-race injury absence, dropped backwards to a disappointing eleventh during the second half of the race, while Kawasaki team-mate West - a backmarker for much of the season - battled to a superb fifth.

Fourth position went to Honda Gresini's Shinya Nakano, making his factory RCV debut. The Japanese had been just twelfth at the end of lap one, but got stronger as the race progressed.

Vermeulen will have hoped for better than sixth, while Stoner's team-mate Marco Melandri scored his second-best result of the season with seventh place, just ahead of rookie Alex de Angelis.

de Angelis completed an all-Bridgestone top eight, a shocking result given that only Stoner failed to finish.

JiR Honda's Andrea Dovizioso was the lead Michelin rider in ninth place - nearly 39secs behind Rossi, whose Michelin-shod team-mate Jorge Lorenzo rode from last on the grid to tenth.

The fallout from the Czech Republic Grand Prix could be profound in terms of Michelin's future in the premier-class, on a day when its leading title contender, Dani Pedrosa, limped home in a disastrous 15th place for Repsol Honda.

Pedrosa - making his race comeback after a hand injury in Germany - finished ahead of only Randy de Puniet, who fell, and is now 65 points behind Rossi with six races remaining.

Czech Republic Grand Prix:

1. Rossi
2. Elias
3. Capirossi
4. Nakano
5. West
6. Vermeulen
7. Melandri
8. de Angelis
9. Dovizioso
10. Lorenzo
11. Hopkins
12. Guintoli
13. Toseland
14. Edwards
15. Pedrosa
16. de Puniet