Though the teenager has suffered a number of technical failures this year and also been on the receiving end of others' over enthusiasm, Webber feels the youngster has made too many mistakes of his own.
"Both of the guys have driven well this year," said the Australian, "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," he continued, "which puts pressure on mechanics getting the car ready. 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," he admitted, “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."
On the other hand, Webber has nothing but praise for countryman Daniel Ricciardo, who is currently fourth in the standings.
"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," he added, "'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."