Jonathan Rea could prove to be a thorn in the side of title rivals Noriyuki Haga
and Ben Spies this weekend by signalling his race win intentions with provisional pole position for the Portimao season finale.
While most eyes were on Haga and Spies for much of the session, neither would experience a stint at the top of the timesheets, with privateer Ducati pair Shane Byrne and Jakub Smrz instead setting the initial pace as lap times tumbled by more than a second.
Reviving memories of his dominant pre-season performance around the Portuguese circuit several months ago, Byrne held the top spot for more than half the session before being deposed by practice pace setter Smrz.
The Czech rider looked on course to complete a dominant day for the Guandalini team until Rea moved top with ten minutes remaining, the Northern Irishman holding the position to the chequered flag.
Spies and Haga, meanwhile, had to be content with third and ninth respectively, the American getting to within a tenth of Rea at the close, while his Japanese rival 'languished' half a second behind.
Having been the quicker of the two during practice, Haga spent much of the session outside the top ten as he focused on race set-up before catapulting to fourth at one stage. However, the championship leader would eventually tumble down the order to be classified as only the fifth fastest Ducati rider on circuit.
Embarking on his final event for Ten Kate Honda before switching to the privateer Althea team, Carlos Checa
backed up Rea in fourth position, just ahead satellite Ducati duo Byrne and Fonsi Nieto, the pair suggesting the Italian bike will at least have strength in numbers at the front this weekend.
Imola and Magny-Cours provisional pole sitter Michel Fabrizio
was the best of the factory Ducati riders in seventh, ahead of fellow Roman Max Biaggi, who was able to pull his Aprilia into the top ten after a quiet morning.
Leon Haslam rounded out the top ten on his Stiggy Honda, ahead of Yukio Kagayama, who slipped from a practice result of third to 11th. Ruben Xaus
and Troy Corser
followed in 12th and 13th for BMW, while Broc Parkes led a trio of Kawasakis in 14th, ahead of Makoto Tamada
and Luca Scassa.
Further back, it was a tough day for the British Superbike alumni, with Tom Sykes down in 18th, Leon Camier 19th, Sylvain Guintoli 22nd and Ryuichi Kiyonari