After throwing away what looked like certain victory in the Qatar season-opener, Casey Stoner was straight back on top of the MotoGP timesheets during Friday practice at Jerez - despite another accident.

Stoner, who had dominated the Qatar weekend only to fall while pulling away in the race, ran up front from the start of the free practice hour in Spain - and held an intimidating 0.671sec advantage as the midway point came and went.

Jorge Lorenzo, riding in front of his home fans and in much better physical shape after the extra time to rest his healing hand, led the challenge to catch Stoner - and had closed to within 0.144sec as the final 15 minutes began.

Lorenzo's progress than stalled, but just as Stoner looked set to complete a perfect session he slid off in a cloud of dust - with two minutes to go - after a lowside from his factory Ducati.

The Australian, whose previous best Jerez finish is a third place achieved last season, walked away unharmed and at least retained his position at the head of the timesheets.

Lorenzo, who had been delighted with his second place at Qatar, confirmed that position on Friday for Fiat Yamaha.

Just behind him, Stoner's team-mate Nicky Hayden made an excellent start with third position - 0.417sec from the top - at a track not previously kind to the 800cc Desmosedici.

Spaniard Dani Pedrosa, who was due to try a new stiffer chassis this afternoon, put his Repsol Honda an encouraging fourth - a clear improvement on his seventh place finish in round one.

Reigning seven time MotoGP champion Valentino Rossi, riding with stretched ligaments in his shoulder due to a motocross accident following his Qatar win, had to be content with fifth place, 0.86sec from the top - a position he held for much of the session.

Fellow Italian Loris Capirossi made it five different machines in the top six by being the final rider within one-second of Stoner, with Monster Yamaha Tech 3's Colin Edwards the leading satellite rider in seventh.

Hector Barbera fell at low speed early in the session, but had already recorded a lap quick enough to keep him in the top six for most of the hour, and eighth by the chequered flag.

Fellow home rookie Alvaro Bautista, seeking his first MotoGP finish this weekend, was a fraction slower on the second factory GSV-R.

After a demoralising 13th and last in Qatar, Marco Melandri began round two with tenth position, while reigning World Superbike champion Ben Spies claimed eleventh at a track he has never previously raced at.

Andrea Dovizioso, who carried the Honda charge in Qatar - culminating in a last gasp third ahead of Hayden - was only twelfth fastest on Friday, ahead of Randy de Puniet (LCR Honda), Mika Kallio (Pramac Ducati), Marco Simoncelli (Gresini Honda), Aleix Espargaro (Pramac Ducati) and Hiroshi Aoyama (Interwetten Honda).

Friday practice:

1. Stoner
2. Lorenzo
3. Hayden
4. Pedrosa
5. Rossi
6. Capirossi
7. Edwards
8. Barbera
9. Bautista
10. Melandri
11. Spies
12. Dovizioso
13. de Puniet
14. Kallio
15. Simoncelli
16. Espargaro
17. Aoyama