Lorenzo might not have been the only rookie on the podium had Andrea Dovizioso kept his JiR Team Scot Honda on two wheels; the Italian made a great start to climb from seventh to third on lap one and stuck with the eventual top three until he fell on lap 16.
With Rossi - whose losing streak has now reach seven races - fading in the closing stages, Dovizioso may have been perfectly placed to repeat his late Qatar pass on the seven-time world champion. Rossi was also handed vital breathing room when Nicky Hayden - who had inherited fourth from Dovizioso and was lapping as fast as anyone - fell just a lap later.
Rossi thus finished five seconds ahead of satellite Tech 3 Yamaha rider Colin Edwards, with John Hopkins enjoying his best race yet for Kawasaki with sixth position after clinging with the leaders for the opening half of the grand prix.
Sixth place went to world champion Casey Stoner, who had struggled with his Ducati in qualifying and dropped back as low as eleventh by lap 15. Thereafter the young Australian mounted an impressive recovery, despite some loose technical equipment rattling against his fairing, to finish two seconds from Hopkins.
James Toseland was unsure of how hard to push during the rain spots that fell for much of the race, but was once again in the thick of the action as he battled with the likes of Stoner, de Puniet and Chris Vermeulen - with whom he had clashed at Jerez - on his way to seventh.
de Puniet fell from his LCR Honda late in the race, while Vermeulen took eighth position - just in front of Rizla Suzuki team-mate Loris Capirossi. Tenth place went to Gresini Honda's Shinya Nakano.
Marco Melandri was 13th on the second factory Ducati, with Anthony West also continuing to struggle, the Australian 16th and last on the second ZX-RR.
Portuguese Grand Prix:
11. de Angelis
15. de Puniet