Carlos Sainz says it is "scary for Renault" how much progress Honda has made in recent races.
Previously, with Ferrari and Mercedes speeding ahead at the front, Renault at least had the edge over F1's fourth-best engine supplier, Honda.
But Sainz, who is switching from the Renault works team to Renault-powered McLaren in 2019, says the situation is changing.
"At Suzuka, I left the Honda cars behind in the race but in qualifying they have taken a step forward. We could not develop in the same way and it's scary for Renault," he is quoted by Speed Week in Austin.
Sainz, however, says there is still hope for Renault.
"We will have a whole new engine next year," he said. "Renault is capable of building an engine that is on the level of Ferrari and Mercedes."
