By lap 3 Porto had more good news when his pit board told him that he had a five second lead, but not so pleased was fourth placed Naoki Matsudo who was given a stop/go penalty for a jumped start.
In those early stages a distinct set of races were forming; Porto versus the racetrack for victory and Rolfo, Melandri, de Puniet, Elias, Matsudo, Battaini, Alzamora, Stoner and Vincent rounding out the pack
But more heartbreak was to follow for Vincent when his engine let go on lap 5, leaving the underpowered Cibertel rider to reluctantly pull off the racing line and into retirement.
Within 1 lap of Vincent's exit, Porto lead was up to an amazing 10secs in what is the Argentinean's closest thing to a home race. In terms of the championship, Melandri held fourth, five places ahead of his nearest title rival Nieto, who was being totaled outclassed by Toni Elias – who was now challenging Rolfo for second.
By lap 10 of the 22 a fully dry line was clearly visible all around the circuit, but such was the humidity that the speeds reached yesterday would never be repeated. While the pack fighting for second had started to spread out, with Melandri holding a 0.8secs lead over the battling Rolfo and Elias, with Porto still 8secs clear up front – but by no means safe.
The status quo at the front continued through the mid stages of the Grand Prix, with Porto out on his own (by 14 secs) and looking odds on for his first GP victory, with Rolfo holding a 2secs lead over Battaini, Melandri and Elias – who would soon have team-mate Nieto breathing down his neck, who himself was under pressure from Stoner and pole sitter de Puniet, who would crash out of ninth on lap 15.
But playing no further part was Roberto Locatelli, who had indeed bravely gambled on a dry set-up, only to be foiled by the constant drizzle sweeping the circuit. The Italian former 125cc World Champion pulled in to the pits and retirement.
Tragedy struck Nieto and his championship hopes mid way around lap 16 when he lost the front of his Telefonica liveried machine at the apex of a medium speed left hander – sending the Spaniard skidding into the gravel trap, whereupon his Aprilia flipped over and over, destroying itself.
Having checked the damage of his machine for himself the fuming Nieto then set out to vent his anger on various inanimate objects that included the tyre wall and various other expressions of disgust as he saw his title hopes frustratingly disappear into the Rio mist.
Fourth placed Melandri was soon given the news via his pit board, and the MS Aprilia rider would surely be on a points collecting exercise from then on as he sought top further bolster his huge points lead.