Valentino Rossi has described Honda's MotoGP form as "worrying" after Marc Marquez gave the manufacturer its second straight victory at Austin.
Marquez cruised to his sixth successive win at the Texas venue on Sunday while Yamaha rider Rossi could do no better than fourth.
It follows Honda's first win of the season in Argentina, which came courtesy of LCR rider Cal Crutchlow, and a strong showing in Qatar where Marquez only just missed out on victory to Ducati's Andrea Dovizioso.
Rossi admitted the situation was a concern, but was positive that Yamaha enjoyed a relatively competitive showing at Austin, with Maverick Vinales second behind Marquez.
"It's worrying, because they are very strong, but especially it's a bike that always go well," Rossi said of the Honda.
"They are competitive more or less in every condition, so it will be hard.
"But here we put two bikes in the top four at a track that doesn't favour Yamaha usually.
"Now it will be important to see how we fare at Jerez, because last year when we returned to Europe, on different tracks where the grip is different, we suffered a lot.
"This year I hope we are more competitive on tracks we like, like Jerez and Barcelona."
Rossi said his target for Austin was to finish on the podium from fifth on the grid, but front tyre issues prevented him from being able to battle Vinales and Suzuki's Andrea Iannone ahead.
"The race was a little bit worse than what I expected," he said. "I hoped to have [2m]05s-high pace, because on Friday afternoon and Saturday afternoon I was on that pace.
"I knew that with that pace I could fight for the podium, and the target was to fight for the podium.
"But unfortunately I suffered more than the others, especially with the front tyre.
"I never suffered in practice but today in the fast corners, I lost too much on the limit.
"So I have to slow down a little bit, try to stay close to Iannone for the podium, but he was stronger than me and at the end I wasn't able to fight."