Jorge Lorenzo's nightmare run continues, with the triple MotoGP champion withdrawing from the Japanese Grand Prix and in serious doubt for next weekend's Australian round.

Lorenzo instantly knew he was in big trouble with his injured wrist at Motegi this morning, pulling into the Ducati pits before completing a timed lap.

Official confirmation of his withdraw came soon after, meaning the Spaniard will fail to score points for the fourth event in a row and could well also miss Phillip Island.

"It's a sad moment for me because I really wanted to race at this track, which is one of my favourites," Lorenzo said.

"Motegi is a circuit that I like a lot, it adapts well to the characteristics of the bike and it was perfect to make a good result. But even after my efforts to accelerate the recovery, I didn't recover as fast as I imagined.

"Yesterday my feelings weren’t very positive and unfortunately today I had confirmation not only of the pain, but also that there was a serious risk of making the fracture worse.

"On hard braking I couldn't push with my left wrist and I had a lot of pain in the left corners and especially in the change of direction. I wasn't fast, I wasn't comfortable and I wasn't safe, so there was no meaning to continue."

The fracture to Lorenzo's left radius bone occurred when he was thrown from his GP18 by a technical failure during Friday practice at Buriram on October 5, but was initially diagnosed only as a 'crack' or hairline fracture which would heal naturally.

As such, by withdrawing from the Thai event, Lorenzo hoped to be fit by Motegi.

But ongoing pain from the arm prompted further checks in Japan on Thursday, the new scans revealing the injury 'looks like a complete fracture' and would therefore be in danger of opening under the stress of riding.

Such an injury would normally be treated by surgery, as undertaken by Moto3 title leader Jorge Martin, who finished third in Austria a week after breaking his radius bone in Brno.

With two weeks having already passed since Lorenzo's injury, it is unclear whether he would benefit much from belated surgery. And with no title to fight for, there is little motive for an early return - especially at Phillip Island, where Ducati struggled badly last season.

But the Malaysian round on November 2-4 is a different story. Lorenzo was fastest in pre-season testing at the Sepang track, which perhaps offers his best chance of a fourth Ducati victory before moving to Honda.

"Now the plan is to go to a local hospital to make an MRI, to understand not only the bone but also how the injury is outside the bone, then take some conclusions," Lorenzo said.

"But obviously, if today I wasn't right, I would not be much better by Phillip Island in just six days.

"I feel really bad for my team and for the fans, but now I only have to be patient and try and recover as best as possible to be ready in Australia or in Malaysia."

The falls at Misano and Aragon (where he suffered foot injuries) and subsequent withdraw from Buriram, Motegi and possibly Phillip Island means Lorenzo could drop from fifth to as low as ninth or tenth in the world championship by Sepang.

Team-mate Andrea Dovizioso was fastest during a rain-interrupted opening day in Japan.