Quartararo qualified fourth at Buriram, but was immediately dropped to 11th after being forced wide at the first corner in the wet contest.
He plummeted to 17th after running wide exiting Turn 4 moments later and could make no further progress up the order, seeing his championship lead wiped out by Ducati’s Francesco Bagnaia – who was third – from 18 to two points.
Quartararo stormed out of the Yamaha garage immediately after the race and cancelled all media duties, with the team at a loss as to explain his woes.
“As you can imagine, that was not the situation we wanted to deal with,” Yamaha boss Massimo Meregalli said.
“We did not talk to Fabio after the race, because he was probably very disappointed and frustrated and he went straight to his office to cool down.
“It’s also difficult for us to judge until we speak to him. We have to talk to him and check the data and see if they match.
“And it’s very difficult to understand. For everyone this race has been a gamble, because having done all the sessions in the dry and then race in the wet.
“But we did the same thing in Indonesia, but there we did the same thing and performed well.
“Here was completely the opposite. It’s very unclear the reason and we need to time to understand.”
RNF Yamaha rider Cal Crutchlow followed - and at one stage passed – Quartararo in that race, and says it was clear the Frenchman was battling the same front tyre pressure issues as he was.
“He’s a good wet weather rider, because last year he came third in Le Mans. This year he was on the podium in Mandalika,” Crutchlow said.
“The bike, honestly speaking, is not the best in the dry, so he’s riding so well in the dry and he’s making the difference.
“And in the rain, everyone is riding as good as what they were but our bike problems are exaggerated even more. So, we need to improve it.
“I could see [he was struggling with the front tyre]. Me and him, the only thing I did was outbrake him.
“The only good thing I could do in that race was brake, the rest was a waste of my time.
“But when you brake hard, you increase the front pressure again. So, you’re in a no-win situation.
“Fabio was turning exactly how I was turning, couldn’t go round a corner. Then you are slow around the corner, so you pick up the throttle and you’ve got no rear grip either. And we know he’s a good wet weather rider, so it’s a shame.”
