Casey Stoner, winner at Qatar for the past three seasons and the Losail race-lap record holder, had to play second best to reigning MotoGP world champion for the fifth day of pre-season testing in succession, as the Losail test began on Thursday night.

The Ducati Marlboro star had been runner-up to Rossi during all four days of previous 2010 testing at Sepang in Malaysia, but the Qatar outing was expected to play more into the Australian's hands.

Stoner put in a late burst of fast laps to lead the field with an hour and a half to go, but Rossi responded in the closing six minutes to lead the day one timesheets by 0.315sec from the 2007 world champion.

Nevertheless, Stoner set four laps in the 1min 55sec bracket, compared with only two for Rossi.

"We tried a few different set-up solutions but the main focus tonight was the tyres," said Stoner. "I used the same set for 30 laps and set some of my best lap times towards the end, so we are satisfied with that. We have also worked on the balance of the bike because the conditions here are very different to Malaysia and I prefer the bike to be more rigid. So far so good."

Stoner will now have just one more chance, on Friday night, to topple Rossi before the 2010 racing season begins, back at Qatar, on April 11.

Meanwhile, Stoner's factory Ducati team-mate Nicky Hayden, who left Sepang with a superb third fastest lap time, had to settle for a less spectacular eighth on the opening night at Qatar.

"Things went well for the first half of the session then we kind of got stuck," admitted the American. "The general feeling of the bike is quite good but I would like to be a step closer to the top guys. The biggest problem is that we're not able to get the most out of the soft tyre - we can't seem to get it working at the right temperature so I have to keep using the harder compound. It happened in Malaysia and we've struggled with it again today at a circuit where the conditions are very different, so it is important we work out the reason."