Valentino Rossi's fourth DNF of the MotoGP season was also his most disappointing, having failed to get beyond the first chicane on the opening lap at a wet Le Mans.

Although starting tenth on the grid, the surprise rainfall meant anything was possible, as illustrated by rookie Alex Marquez riding from 18th to 2nd.

But Rossi's race was already over on entry to the first left-hander when he lost the rear of his M1 and slid off.

"It's a great shame for today because to crash like this at the first corner is the worst thing, also without making some laps to understand the feeling with the bike and my potential," said the Monster Yamaha rider.

Rossi's fourth DNF in nine races means he has already suffered the same amount of non-finishes as during the whole of last year's 19-round season.

The last time Rossi failed to finish more than four races in a world championship campaign was in the 250cc class, in 1998.

"It's a difficult moment. I am also a bit unlucky, because in the last three races I didn't take any points even if my speed was quite good, especially during the practice, so this is bad," said Rossi, who is now 13th in the world championship.

"For the championship, it's very difficult because for me these last three tracks were good on paper for performance - Misano, like we saw in the first race, and also Barcelona especially and Le Mans usually I'm strong.

"So we needed to take points because now we go to Aragon and Valencia for four races that on paper are very difficult for us and for me.

"But it will be also more challenging to try to be competitive, strong, even if the track is not fantastic. We will see."

If it was any consolation to Rossi, the other Yamahas also had a tough time on Sunday. Fabio Quartararo and Maverick Vinales finished ninth and tenth while Franco Morbidelli crashed out.

"Historically in these half-and-half conditions we suffer, I mean today was wet but not fully wet. It was not dry enough for slicks, but there was not standing water on the track," Rossi explained.

"Usually when it's full wet we are not so bad with the Yamaha. But in these half-and-half conditions, wet but not completely wet, and also when it's dry enough for slicks but not completely dry, the M1 suffers.

"It suffers for me in acceleration, we lose a lot because we don’t have enough rear grip and it's difficult to manage the bike."

But it could have been a very different day for Yamaha if the rain had stayed away, with all four M1s at the top of the timesheet in final practice on Saturday.

"It's a great shame also for Yamaha because everybody expected a dry race and in the dry the M1 worked very well, during practice all four M1s were strong and we can make a good race," Rossi said.

Given the difficult circumstances, the 41-year-old praised world championship leader Quartararo for keeping a calm head and doing his best to limit the damage.

"Today he did a very good job because in these conditions it looks like with the Yamaha we suffer, so he took some points, stayed quiet, didn't make any mistakes and did a good job, very important for his championship," said Rossi.

"I think also that the victory in Barcelona last week was great, his best, because the conditions were not easy. So I think that he will be very strong until the end of the year."

Quartararo now holds a 10-point lead over Suzuki's Joan Mir and 18-point advantage over Ducati's Andrea Dovizioso heading into Aragon next weekend. Vinales is one point further back, in fourth.