The Yamaha factory rider was fastest in the dry FP2 on Friday, and fourth on Saturday morning in FP3, which was wet.

However, Vinales was 11th in a wet-but-drying second part of qualifying, marking his worst grid position since last year's Phillip Island race.

The Spaniard was unable to explain his sudden lack of competitiveness, which saw him end up more than two seconds slower than pole-sitter Johann Zarco's Tech 3 Yamaha.

"In FP3, I was feeling great so I don't know, I was feeling good, very good rhythm, doing good laps," said Vinales. "Then suddenly in qualifying I didn't have any feeling.

"I don't know if the track was drier or something but no feeling in qualifying with both tyres. Especially the rear on the entry of the corner and in the middle."

Vinales said there was less water on track in qualifying compared to FP3, but still couldn't go faster without crashing.

"I think there was a little bit less water on the track, but I don't know the reason why I got no feeling to go fast.

"Even if it was sometimes a little bit dry, I couldn't go faster because I felt I'd crash every time. This morning I felt much more confident."

The 22-year-old added he was finding it difficult to stay motivated after a result like this, especially as he thought he could challenge for pole.

"This isn't a good starting position when you are fighting for the championship.

"Another result like this didn't give me the motivation. When you finish FP3 thinking I can go for the pole in qualifying and then you are 11th, amazing."

Rossi: new chassis works well in wet

While Vinales struggled in Q2, Rossi was in the thick of the pole fight for much of the session, albeit ending up missing the front row in fourth place.

While the Italian admitted the top three had stronger pace, he was pleased with how his new chassis was behaving in wet conditions.

"Positive day for us because I was very curious to try the new chassis on the wet because on the wet with the 2017 bike I suffer a lot," Rossi said. "The feeling is not so bad because I was competitive this morning.

"[In qualifying] it was a shame for me to lose the front row, but very important to start from the top five, I am in a quite good position.

"We have to work a little bit because on the wet in the last laps the top three was stronger than me, but I feel good and this is very important."

"I hope for a full dry [race] tomorrow and also for a dry warm-up to try to improve the pace, because yesterday was not so bad but it wasn't enough to fight for the podium."