After a fall in qualifying, Valentino Rossi climbed from ninth to sixth early in Sunday's Thai MotoGP.

But the Italian's progress then suddenly plateaued, followed by a decline to eighth - after being overtaken by the Suzukis of Alex Rins and Joan Mir - where he would ultimately finish.

As so often this season Rossi was hit by a loss of rear grip, this time leaving him last of the Yamaha riders, 19-seconds behind Petronas runner-up Fabio Quartararo.

"Unfortunately, the race was very similar to the last races. After some laps, very early, I start to suffer with rear grip" Rossi said. "I lose grip, lose performance and I have to slow down. It was another difficult race."

Rossi was especially disappointed after being able to hold a competitive pace on used tyres in morning warm-up.

"It is a shame more because this morning with the used tyre after 19 laps I did some good lap times, so I expected to do a quite good race," he said. "But unfortunately with the same tyre, but new, in the race we suffer.

"More-or-less it's always the same. In the last races we have always that type of problem."

The current pattern of fading in the race is the opposite of what has been expected from Rossi for much of his record-breaking career, when he would often pull-out his best form of the weekend.

"Every time I am on the edge of the tyre I suffer very much," Rossi explained. "Silverstone was good but anyway also in qualifying it's not fantastic, but especially in the race we suffer.

"But anyway, we have another four races, we made a long meeting here and we will try something next time in Japan to be more competitive to the end of the season.

"We have something to do because today sincerely the first three were faster, but in the warm-up I was good with the used tyre. So I thought that for example I can fight for fourth with Dovi and Rins. But unfortunately not."

Rossi remains sixth in the world championship, but has now slipped 18 points behind team-mate Maverick Vinales (third at Buriram) and is just two ahead of rookie Quartararo.

Asked about how important the young Frenchman is to Yamaha's future, after battling Marc Marquez to the final corner of the race, Rossi said: 

"Yes very important. I expect that he can be very fast because he was always very fast from when he was young. But nobody expected like this, so he did something special and it's great and I think [in 2021] everybody will try to get Quartararo on their bike.

"And for sure Yamaha will want Quartararo, yes."