Mark Webber claims Max Verstappen is too "flaky" during the build-up to races on Friday and Saturday, and that itself is having a negative impact on the team as they have to rush to repair and rebuild his car for Sunday's race.
Webber does however believe the young Dutchman has performed incredibly in the races and only reliability issues – of which he has had several – are the reason he's so far adrift of team-mate Daniel Ricciardo in terms of points.
"Both of the guys have driven well this year, but Max has probably been a bit flaky in terms of the build-up to the races through the weekend, he's been going off the road a lot on Friday and Saturday, which puts pressure on mechanics getting the car ready," Webber told Red Bull Australia.
"I'd like to see him on the road a bit more, but he's pushing the limits.
"When it comes to Sundays, he hasn't made many mistakes at all, it's been a lot of high-profile reliability retirements where he's lost a truckload of points, so that's been hard for him to swallow."
Reviewing fellow Australian Ricciardo's performace this season, Webber believes he's got the most out of what he's been given, blaming the Renault engine for Red Bull's lack of absolute pace to put them on terms with Mercedes and Ferrari.
"Daniel is just so solid on Sunday afternoons, he's the most reliable driver in F1 in that you know what he's going to deliver week-in, week-out.
"He's always got the most out of what they've given him and it's hard to see how he could have done much more.
"We all expected such great things from this car this year, but it came out the box very poorly. They had a lot of catching up to do.
"With Renault, it's unfortunately a little bit of a broken record, 'we haven’t got this, we haven’t got that' – it's been going on for five years. [Red Bull] have to make a car a second faster than everyone else, maybe."
