Maverick Vinales has expressed deep concern over the seeming return of the old grip problems that have plagued him since he joined Yamaha's MotoGP team.

The Qatar race winner could only muster 11th place in yesterday's Portimao race and inherited that after a number of riders crashed out after scything his way to the back of the field on lap one.

"Today was difficult, difficult race. I cannot explain why, the feeling was really similar during all the weekend, very low grip, just I had good grip on the last tyre in qualifying which made a huge difference," said Vinales, speaking at the track.

“If they didn’t cancel my lap, it was to be in the pole position. So, basically all weekend we were struggling, we didn’t find out why.

“But it’s time to check, it’s time to see and to improve because on the other hand we will be in the same issue as every year.

“We start winning everything and then little by little we slow down. This is not positive. I am especially worried because it’s a tough season to go like that.

“It’s hard to keep the focus and especially the motivation when you see yourself you could win the first two races, and then you arrive to the next track and you struggle to be in the top 10.

“Fortunately, some riders crashed and allowed us something better."