Ricciardo's smile has Hamilton on edge

Australian Daniel Ricciardo's trademark smile has four-time world champion Lewis Hamilton on edge ahead of the Australian Grand Prix in Melbourne.

Mercedes' Lewis Hamilton feels Red Bull driver Daniel Ricciardo is smiling for good reason. (AAP) Source: AAP

He is synonymous with his smile but Daniel Ricciardo's trademark pearly whites have four-time world champion Lewis Hamilton on edge.

Mercedes gun Hamilton is clearly wary of Red Bull's Ricciardo after seeing him flash his impressive grin a great deal at Albert Park ahead of Friday's practice.

"Daniel has been smiling quite a lot today, so I think you are going to be surprised this week just how competitive Red Bull are," Hamilton said ahead of Sunday's Formula One season opening Australian Grand Prix in Melbourne.

Ricciardo's Red Bull is expected to join Sebastian Vettel's Ferrari to challenge Mercedes this season after Hamilton's all-conquering team clinched the last four drivers' and constructors' championships.

Hamilton got a taste of what he expects to come in Melbourne at recent F1 testing in Spain where Ferrari recorded the outright fastest lap times and Ricciardo wasn't far behind.

"There is a lot of hype around our team which I think is very difficult to take much notice of because the last test was a little bit distorted with the track and the way it was," Hamilton said of testing.

"Everyone was on different types so I'm excited to see how everyone fares up when we all get into practice (on Friday)."

While well aware of Red Bull's threat, Hamilton clearly didn't rate 20-year-old Max Verstappen's chances.

The Dutchman defied his age to complete his first full season with Red Bull in 2017 with two race wins to finish sixth overall, just one spot behind teammate Ricciardo.

But Hamilton was reluctant to give Verstappen a rap when asked if the youngster could threaten for a title.

"I don't have an answer," Hamilton said.