Red Bull does believe Mercedes is currently struggling for performance and thinks a lack of a 'B-team' could be to blame.

The German manufacturer has made a steady start to pre-season testing with Valtteri Bottas acknowledging the W10 has been suffering from handling issues in certain issues.

By comparison, Ferrari and Red Bull have had a pretty seamless start, particularly considering the Milton Keynes-based outfit is in the early stages of a new engine partnership with Honda.

"Ferrari is the bar at the moment, very clearly," advisor Helmut Marko told Auto Bild. "The car is impressive. How far ahead they are of us is hard to say. But what we can say is that we are clearly ahead of Mercedes."

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Certainly, a key factor for the smooth transition has been the experience Red Bull gathered with their junior team, as the Austrian noted.

"Toro Rosso did some development work for us with Honda and probably even sacrificed some races for it as well," Marko said. "But that makes them stronger in 2019 too. They also benefit from it."

Ferrari too has used their alliances with Haas and Alfa Romeo to test engine parts before putting them in the Prancing Horse, but Mercedes' customers, Racing Point and Williams, have been more reluctant to follow that path.

"I think Mercedes is a little alone there," the Red Bull advisor stated. "I cannot imagine that the influence Mercedes has on its customer teams is so great."

Regardless, world champion Lewis Hamilton also acknowledges 2019 is shaping up to be his team's toughest title defence yet.

“I’m competing with everyone. I don’t know who’s going to be quickest. I think you can’t say just Ferrari," he said last week.

“I don’t know where the Red Bulls are. I’m hopeful that there’s going to be more teams involved, but who knows what people are going to bring up when we get to the first race.

“It’s been a difficult winter for the guys back at the factory,” Hamilton added. “I could see it and I’ve heard from the guys, probably the most difficult one particularly with the rule change once again.

"But if anyone can do it, I truly believe it’s my guys. We are the only team to have won a championship in a cross over of a rules situation.”