Lando Norris says his previous teammate was better than Daniel Ricciardo at adapting to a difficult-to-drive Formula 1 car.
Australian Ricciardo's struggle to get up to speed at McLaren this year was amplified on the streets of Monaco in Thursday practice.
"You need a very specific driving style to be fast with this car," said the struggling 31-year-old, whose teammate Norris has just received a new two-year contract.
Ricciardo, who is thought to currently earn millions more than Norris, is also staying at McLaren next year.
"Daniel is very, very fast when he has a car around him, when everything suits him," Norris, 21, said at Monaco.
"But as soon as there's a couple of problems, he tends to lose that bit of confidence, just as most drivers do. That's just something that some drivers have more than others. It's a confidence thing," said the Briton.
"From what I've seen so far, he wants a car that really suits him, maybe that little bit more."
According to Norris, Ricciardo's predecessor Carlos Sainz - who is also getting up to speed in 2021 after switching to Ferrari - is better at adapting to a new car.
"Carlos was good at driving a car which wasn't always that nice to drive," he said. "He was very good at that.
"I think that's just one of the things I have learned at the moment."