Former Red Bull driver Mark Webber has described Max Verstappen as being "a bit flaky" this season, saying he'd like to see him "on the road" more often.
Verstappen has had a disappointing first half of the season, with just 67 points from the first 11 races compared to teammate Daniel Ricciardo's 117. A series of retirements account for most of the gap, with reliability issues resulting in DNFs at three races and first lap collisions out of his control causing DNFs at another two.
But Webber points to Verstappen's performances during practice sessions and the build-up to races as an area to improve.
"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," he told Red Bull's website. "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."
Webber on Alonso
But Webber highlighted McLaren-Honda's inability to give Fernando Alonso a competitive car as the biggest disappointment of the year.
"It's been a big shame for Formula One, a big shame for Honda, a big shame for McLaren. They loaded their guns up and got Fernando back there waiting for the engine to fire, but it hasn't happened.
"He's been biting his tongue for the last 24 months, and he can't drive the thing any harder. His stock is still incredible, and on Sundays he's probably the best in the world. That's the frustrating bit."
Hamilton the best qualifier since Senna
After Lewis Hamilton beat Ayrton Senna's record of 65 career pole positions this year, Webber believes qualifying has been the Mercedes driver's key strength this year.
"Both he and Seb [Vettel] have driven awesome this year, and Lewis particularly in qualifying has been very strong. He's the best since [Ayrton] Senna over one lap -- he's very special on Saturdays.
"I think he has respect at the top level for two to three guys on the grid because he's on such a high level -- Seb and Fernando (Alonso) probably, maybe two or three others. He's in the peak of his career, the hunger and passion is at its maximum, and he likes to put a bit of drama, a bit of heat on himself to go and deliver. He enjoys that and it seems to bring out the best in him."
Speaking about the most controversial collision of the year between Vettel and Hamilton at the Azerbaijan Grand Prix, Webber described it as a "weak moment" for the Ferrari driver but not a dangerous manoeuvre.
"Baku was a crazy rush of blood [for Vettel] with the re-start procedure, and there were obviously some mind games going on that day, which is totally standard. He had a weak moment where he elected to pull alongside Lewis and give him a little rub. It wasn't ideal and didn't look great, and he certainly regrets it. But at the end of the day, it was not exactly dangerous, it just wasn't a great example. You'd be in more danger crossing the street in Italy than that ..."