Sebastian Vettel has raised his game this season following his Formula 1 title, according to Red Bull technical chief Adrian Newey.
And Newey reckons Vettel's improved form explains the gap between the German and his teammate Mark Webber, who Newey believes is not driving any slower than last year.
"Sebastian will often work late trying to understand how the car is working and how he can improve," Newey told Britain's Guardian newspaper. "He's a quick learner and rarely makes the same mistake twice. At the moment, he's really on top of his game. So far the gap between Sebastian and Mark has been bigger than last year.
"It's certainly not a case that Mark has been driving any slower – that's for sure. Mark's just taken a bit longer to adapt to the Pirelli tires but the gap is closing."
Newey is still hoping Webber stays on at Red Bull, praising the contribution made by the Australian.
"I'm hoping Mark continues next season," Newey added. "Apart from being a great person, his contribution has been significant. He's been a pillar of the team from the start. Seb is very perceptive in his feedback in some regards and Mark is very perceptive in other areas. We listen to both and it helps the car."
The Briton, who won titles with McLaren and Williams, also admitted that clinching the crowns with Red Bull last year was the most satisfying of them all.
"In many ways, winning the constructors' and the drivers' titles with Red Bull last year was the most satisfying of all. When I left McLaren to come here in 2006 lots of people said: 'Newey's bitten off too much this time. He's going to fall on his face and wreck his career.'
"I try not to be affected by what other people say, but everything we've achieved over the last five years has been amazing."