Championship leader Jorge Lorenzo heads into qualifying for the 2010 United States Grand Prix as the tentative rider to beat after going fastest in second and final free practice at Laguna Seca.
The Spaniard fended off the challenge of Casey Stoner in a tight session, the FIAT Yamaha rider setting his pace setting lap of 1min 21.763secs at just over the half-way mark to keep his rival at bay by a marginal 0.063secs.
Still, Lorenzo could have gone faster had he not been baulked on what was set to be his best lap by fellow Yamaha rider Colin Edwards, thus ensuring Stoner's effort from FP1 remains the quickest lap of the weekend thus far.
The top three were closely matched with 2009 winner Dani Pedrosa getting the edge on Repsol Honda team-mate Andrea Dovizioso in third, the Italian three tenths further adrift in fourth.
A swift late lap from Ben Spies saw him leapfrog Valentino Rossi, the hobbled reigning champion nonetheless completing 34 laps as he wound up some six tenths adrift of his team-mate.
Colin Edwards made it four Yamahas inside the top seven as he finished ahead of countryman Nicky Hayden in eighth, while Hector Barbera ended up as the top 250cc graduate in ninth after his final lap got him ahead of Aleix Espargaro.
Outside the top ten, Marco Melandri was 11th fastest, ahead of the Suzukis of Loris Capirossi and Alvaro Bautista, the Rizla team making solid progress after a difficult first day around the Californian circuit.
Having crashed in FP1, Marco Simoncelli stayed upright to set the 14th best time, ahead of Mika Kallio, who was the only rider to take a tumble during the session. Meanwhile, in the battle of the 'replacement riders', LCR Honda's Roger Lee Hayden got ahead of Interwetten Honda's Alex de Angelis.