Facing his first chance to wrap-up the MotoGP title this weekend, wet weather during Friday practice at Misano once again sent Fabio Quartararo sliding down the timesheets.

The Frenchman, who holds a 52-point advantage over Francesco Bagnaia with only 75-points remaining, was just 18th in morning practice (+3.1s) but more concerned by 16th in the afternoon session (+1.792s).

While most riders improved as the track began to dry, Quartararo's best time came on his 9th of 19 laps.

The Monster Yamaha rider was running 1m 44s at the end of the session, when a dry line began to appear, while the fastest riders in the mixed conditions were setting low '42s.

Quartararo certainly wasn't the only M1 rider to struggle. In fact he was the fastest, with Franco Morbidelli, Valentino Rossi and Andrea Dovizioso all behind him on the timesheets as they battled a chronic lack of rear grip.

"To be honest, I'm happy about full wet, because this afternoon, straight away I felt really good on the bike, and until we stopped, we were in P7," Quartararo said. "And then as soon as it dries, you can ask all the Yamaha riders, it's like you are riding a totally different bike.

"The bike doesn't turn, the bike doesn't want to pick up, the bike has no grip. All the defects you can have in these kind of conditions are there.

"But in the full wet, I would not say super happy, but we made a big step since last time we were here, because we had a chance to ride in COTA, and we made a massive change and it was good.

"So in the mixed conditions, I don't know why we are that bad."

Team-mate Morbidelli said: "The feeling is that the grip fades away instead of increasing. When you don't have grip, you cannot ride well or fast. This is what happens to us. Instead of when the track gets dry, instead of the grip getting higher, it's worse.

"It's our problem, it's more Yamaha's problem than Michelin. I'm sure, because everybody else is able to be fast."

Should wet weather return on Saturday morning, as forecast, Quartararo - who threatened Bagnaia for victory in the dry at last month's first Misano round - will have a fight on his hands to avoid a rare appearance in Qualifying 1.

"I gave my maximum to try to be in the top ten, which was the goal. But as soon as we stopped for the medium front, with a new soft rear, I was spinning so bad. I had no grip, we were almost one-second slower than the lap time I had before, even though the track was more dry," Quartararo said.

"And basically, a lot of riders that were not super strong in full dry, they made a massive step in the mixed conditions.

"We need to understand why we are so bad in that condition. But not only me, it's all the Yamahas are struggling in those conditions. So it's something that we need to find and try to improve.

"Something is going wrong, clearly. Because in the mixed conditions we need to find something. And on the full wet we know that the Ducatis are really difficult to beat."

Petronas Yamaha's Dovizioso, a triple title runner-up for Ducati, had also confirmed the vast difference to the Desmosedici in the wet.

"Right now, to beat Ducati, he explained to me that it is quite difficult with our bike," Quartararo said. "So I think we don't need to dream too soon on the wet. But in the dry, I think we are doing a great job.

"I spoke to Andrea, and he knows better than me about riding the Ducati, but what I see from the outside, it's clear that it's also [the case] from inside. So we need to make that step. We improve every time we go on track, but it's not enough."

Bagnaia, eighth fastest, was one of five Ducati riders in the top ten on Friday.