It already looks like a case of 'when' not 'if' World Superbike champion and 2010 MotoGP rookie Ben Spies will attack the MotoGP big four, after the severely jet-lagged American finished his first test on the 2010 Yamaha in fifth position.

The Monster Yamaha Tech 3 rider had been twelfth and sizeable 1.7sec off the pace during his first ever day around the long, fast and technically demanding Malaysian Grand Prix.

"Right now it's just me. There's a good half-a-second just in myself," said the Texan, whose journey to Sepang involved stops in Italy and Dubai.

But with a better night's sleep, and an improved braking style, Spies slashed 0.9sec from his best lap time on Friday to be both the top rookie at the test and top satellite rider - ahead of even experienced team-mate Colin Edwards.

Indeed, Spies was beaten only by MotoGP's four 'aliens' - a nickname given to Valentino Rossi, Casey Stoner, Jorge Lorenzo and Dani Pedrosa by Edwards, due to their domination of the 800cc era.

Those four riders have won all but three of the MotoGP races held since the start of 2007, but many believe Spies - a WSBK champion at his very first attempt - has the talent to join MotoGP's top table.

At Sepang, which is 5.548km in length, Spies needed a further 0.444sec to match fourth-placed Pedrosa (Repsol Honda) and was 1.341sec behind Fiat Yamaha's reigning world champion Rossi.

"I rode as good and as hard as I could considering how I've been feeling," said Spies before leaving Malaysia.

"I'm not wanting to make any excuses but I didn't feel really good with the jetlag. It was still a good test because I learned a lot about improving my riding and adapting my style to suit the Yamaha MotoGP bike.

"It is hard to break some of my old superbike habits at the moment but I made some big improvements in a couple of places on the track where I was really struggling, particularly in the braking. It started to feel more natural today and I got down to some decent times on race tyres.

"I was a second faster than the first day, so we made some good progress but this is a really difficult track to learn. This track is really long and really wide, but I got to a respectable pace. I've said it a load of times but it's a learning process and every lap I'm learning.

"My guys at Monster Yamaha Tech 3 though have been brilliant again. We're all putting in a lot of effort and I'm pleased with the steps I've made."

Edwards was 0.2sec slower than Spies as he evaluated several different chassis and swingarm setting options.