Valentino Rossi will head into his first MotoGP race for Ducati, in Qatar next Sunday, having been just 13th fastest on the final night of pre-season testing - and no higher than eighth throughout the winter.

The seven-time MotoGP champion finished the second and final night of pre-season preparation at Qatar's Losail circuit as only the fourth-best Ducati rider - with hopes of a set-up breakthrough hindered by a second crash in as many days.

"I'd say that today was pretty challenging: the weather conditions were much tougher than yesterday, and I had another crash when I slipped on a white line," said Rossi, who was faster than just four riders on Monday. "Fortunately, I just fell over on the ground - it was nothing serious."

Rossi is still struggling to make the Desmosedici turn, partly due to his healing shoulder - which became a real problem towards the end of the test. The #46 completed 50 laps on Monday, the best of which was 1.307sec behind fastest man Casey Stoner (Repsol Honda) and had to abandon a race simulation.

"The real problem was that at about an hour and a half from the finish, I started to lose strength in my shoulder, and I just couldn't push anymore," said Rossi.

"It's a shame, because I had just done my best time, and I may have been able to drop it a little more from there. Instead, we didn't even mount the two soft tyres that we had.

"I started on a long run, but I stopped because I was losing tenths lap after lap.

"Let's say that we're not as far back as it looks, although we still have a lot of work to do, regarding both the bike and myself, because the shoulder is evidently not yet able to bear two such intense days of testing.

"Between now and Thursday, I'll do some light exercise and have it massaged, and then we'll see," concluded Rossi, who won last year's Qatar race for Yamaha after Stoner fell from the lead.

Rossi's team-mate Nicky Hayden was ninth fastest and just over one-second from former team-mate Stoner.

"We tried some different options and got a little bit better, but not like we really wanted to," said Hayden. "I did two longer runs and was able to string together some laps at a decent pace, on both hard and soft tyres. I ended the day with a crash in Turn 2, where a lot of guys have gone down this week. I just lost the front end.

"Anyway, that's enough testing, because this weekend it will really mean something. We know it's going to be a tough one, because everyone is pushing so hard, but we'll do our best to come in here and make a good showing."

Pramac's Randy de Puniet surprised by leading the Ducati challenge in sixth place (+0.758sec), with Aspar's Hector Barbera also ahead of Rossi, in eleventh.