A nagging shoulder injury may force Valentino Rossi to bring an early end to his injury-plagued MotoGP season after next month's Australian Grand Prix.
The seven-time world champion says his performance at Victoria's Phillip Island circuit, where he has won five times, will be crucial to his decision.
Rossi's right shoulder is now a bigger problem than the broken leg he suffered in June which forced him out of racing for 42 days midseason.
The Italian damaged a shoulder tendon in a motocross crash in April and the injury has failed to respond to intensive treatment.
Surgery following Phillip Island would require two months rehabilitation and mean missing the final two races in Portugal and Spain.
A suffering Rossi finished a distant sixth, 27 seconds behind race winner Casey Stoner, in yesterday's Aragon Grand Prix in Spain.
He now faces a brutal physical period with three consecutive flyaway races.
The Japanese GP, which takes place in just under two weeks, is followed on consecutive weekends by Malaysia at Sepang and then Australia (Phillip Island) on October 17.
"Phillip Island, and Sepang are good tracks that will be important to understand the extent of my injury in relation to the final two races," Rossi said.
"Both these tracks are easier for me but unfortunately Motegi (Japan) will be the worst for my shoulder. But I have decided to try these three races.
"I only have 50% power in my shoulder, it is now a bigger problem than my leg.
"I cannot ride like I want. I don't want to have surgery but the pain is constant and the situation has not improved."
With its flowing layout and predominantly left-hand corners Rossi says Phillip Island will ease the stress on his right shoulder as he makes a crucial fitness assessment.
Japan's compact Motegi circuit is a non-stop combination of short straights, hard braking, and tight right-hand corners that Rossi fears will punish his shoulder.
Rossi had anticipated shoulder surgery at the end of the season but now realizes that he is unable to fight for race wins and pushing forward the surgery would give him more time to be ready for his move to Ducati in 2011.
Rossi has won just one race this season, the opening GP in Qatar, and missed four races after suffering a compound fracture to his right tibia at Mugello in June.