But the race wasn't over yet. Just behind Stoner, Lorenzo proved he isn't afraid to take on illustrious team-mate Rossi as the reigning 250cc world champion ran the Italian right to the edge of the track as he retook second position.
Lorenzo was predicted to run a strong race and the #48 kept his hopes of a dream debut victory alive by closing quickly onto Stoner's rear wheel - then sticking with him as the pair pulled clear of Rossi, who was left facing increasing pressure from Pedrosa, Dovizioso, Toseland and Edwards.
Stoner eventually broke Lorenzo's spirited challenge with seven laps to go, then built up a five-second victory margin by the time he took the chequered flag, but the Australian will surely be seeing a lot more of his former 250cc rival in the races ahead.
Meanwhile, the battle behind was much closer, with Rossi clearly struggling for grip during the second half of the race and, after holding off Pedrosa for several laps, the Spaniard out-accelerated Rossi onto the main straight to take third place on lap 15.
Valentino was unable to respond and instead had his hands full trying to defend fourth from rookies Dovizioso and Toseland. Dovizioso plucked up the courage to dive inside The Doctor on lap 20, but Rossi quickly swatted his young countryman back to fifth.
However, the 250cc title runner-up - himself under pressure from Toseland - repeated his hairpin move on the very last lap and this time Rossi couldn't counter attack, Vale crossing the finish line just 0.017secs behind the satellite Honda rider.
Toseland completed a very impressive grand prix debut by finishing a fraction behind Rossi in sixth, with team-mate
Colin Edwards seventh after a much more 'quiet' than his one-second deficit to Toseland might suggest.
Of the top seven riders, only Stoner and Rossi were on
Bridgestone tyres and - despite Stoner's victory - the Japanese manufacturer's pre-race fears over the cool temperatures seemed to prove accurate, with the last seven riders all on Bridgestones.
