Maverick Vinales says he fears catching Marc Marquez to win this year's MotoGP title will be "impossible" with Yamaha's current level of competitiveness.
After taking a second straight pole position at Aragon, Vinales' championship hopes took a dent as he trailed home to a fourth-place finish for the second race in succession.
With Honda rider Marquez taking his fifth win of the season, Vinales is now 28 points behind the championship lead with 100 left to play for in the remaining rounds.
The 22-year-old says that the Yamaha bike has to be improved for the last four races if the team still wants to have a shot at the title.
"If we want to win, we have to improve the package," said Vinales. "Every race that passes, our options become more and more limited.
"I woke up thinking about winning [on Sunday], but after giving my 200 percent, you can see that I did not catch them.
"To fight for the championship this way will be very difficult. I had no grip in the rear. If we can find the traction and we find it now, we can fight. But if not, [it will be] impossible.
"We always give the maximum and more, both me and Yamaha, it could already be seen. With the package we have now, it is difficult to think that we can recover [almost] 30 points."
Copied rivals' tyre choice
Vinales used the hard rear tyre during despite never trying it prior to the race - and admitted that his rivals picking that tyre was what convinced him to gamble on it.
"If I practiced on Friday [in the dry] I wouldn’t have gone with the hard," added Vinales, who was struggling with rear grip during the race.
"But our opponents chose the hard tyres, except [Andrea] Dovizioso, who normally uses the soft ones."
"Anyway, I think it was the correct choice because we didn’t have a lot of experience with the tyre. But we didn’t know clearly, the laptimes were really slow this morning, so we decided to do it.
"Once it was decided, I think we did our best because on the first laps I was really slow. I was lucky as well I could manage well my tyres until the end, some opponents drop a lot."
Additional reporting by Oriol Puigdemont