Horner: 2019 F1 aero and tyre changes hit Red Bull's strengths

Although the team is now making good progress with its car, and Max Verstappen is the Mercedes drivers' closest challenger in the world championship, Red Bull has faced some struggles in getting on top of its RB15.

Team principal Christian Horner thinks Red Bull has suffered particularly from the move to thinner tread tyres and the front wing rules revamp introduced to boost overtaking.

"It is probably a combination of the two," he explained about the factors that have held Red Bull back so far.

"Obviously there's 25% less rubber on these tyres and they're stiffer, and we were very good on the tyre at the end of last year.

"I also think the concept of aerodynamics that we've evolved over the last few years was obviously very sensitive to the front wings, so we're just having to rebalance that and refocus that."

Horner thinks the key now is steady progress with both the Red Bull chassis and the Honda engine.

"It's all about evolution and Honda are making good progress," he said.

"Their reliability compared to previous years has been fantastic. Performance is strong.

"But the others don't stand still either."

Horner believes the 2019 title battle is effectively over, saying "I think it's very much a Mercedes championship - after five races they're three points off of maximum score".

But while not dreaming that Red Bull-Honda can close down Mercedes in 2019, Horner has no doubt that the champion team's current supremacy will end.

"Anybody can be beaten," he said. "Formula 1 is all about teamwork, it's about the biggest teams in the world.

"Mercedes, at the moment, are on the crest of a wave but that never lasts forever.

"Our job is to ensure we have all the tools and capabilities to take that challenge to them in the coming years."