Jorge Lorenzo blamed the poor handling of his Yamaha for his disappointing ride to seventh in Sunday's MotoGP race at Le Mans.
The defending champion ran third early on behind Andrea Dovizioso and race winner Dani Pedrosa but dropped back substantially as the race progressed.
The Spaniard, who is now 17 points behind his compatriot Pedrosa's Honda in the championship, said he was struggling everywhere on the circuit and he would have crashed if he had pushed any harder.
"In the beginning of the race the bike was not the same as warm up but not so bad and I could follow Dovizioso and Pedrosa," said Lorenzo, who dominated last year's wet race at Le Mans. "I was losing a lot in some areas of the track but recovering in others.
"Then after three or four laps the bike got worse and I got problems everywhere - in the braking because in the middle of the corner I didn't trust the rear tyre; and in acceleration because the rear was spinning so much. I couldn't do much more without crashing."
Yamaha team manager Wilco Zeelenberg said he was relieved to see his rider make the finish.
"If you don't feel safe and the bike slides, then it's difficult to finish races like this," he said. "We will concentrate on what the problem is because we can't give an answer now. The most important thing today was not to crash."
Less fortunate was Lorenzo's teammate Valentino Rossi, who lost control of his bike while defending fourth from Ducati's Nicky Hayden.He recovered to finish 12th, and said the team would take heart from the strong pace they showed for the first half of the race.
"In that corner, I didn't arrive too fast and didn't feel any mistake but I felt a bump and lost the front," he explained. "It's a pity because we lose points and especially the chance to try to make a good podium here. The important thing is that today we were fast, so we will see next week."