Carlos Sainz has hailed the improvement made by McLaren's engine supplier Renault over the winter.
After years of struggling with customer Renault power, Red Bull is delighted with its switch to Honda for 2019.
But Sainz says Renault - now McLaren's customer supplier - has really improved since last year.
"I've been in F1 for four years, and I was always 10kph down on the straights," he told El Mundo Deportivo newspaper.
"But in Melbourne I was only 2-3kph off the best teams, which is a really encouraging situation," Sainz added.
He said Renault is now on the right track in terms of competing eye-to-eye with Mercedes and Ferrari.
"It seems that they have clear ideas about how to develop the engine during the year, which also gives more of a positive attitude," said Sainz.
"I praise Renault in that sense because finally it seems that they have taken the step we needed two years ago."