Sebastian Vettel has been backed to emerge from one of the worst slumps of his Red Bull career.

On the occasion of his 100th grand prix for the team on Sunday, the four-times champion was forced to retire after just five laps of the Monaco Grand Prix with a turbo failure.

It was Vettel's second retirement in six races this season, which put in context is almost a crisis for the 26-year-old bearing in mind in the previous three years he had only suffered three.

Now in his sixth season with Red Bull, only once during that time has Vettel endured a longer winless drought than at present, back in 2012 when he failed to take the chequered flag for nine races.

With Vettel's reliability issues the fault of power-unit supplier Renault, team principal Christian Horner said: "You need to speak to them about the reasons, but it's obviously frustrating.

"The weekend was pretty tough on Seb, and he did doing nothing wrong.

"He's smart enough to recognise that, so like any sportsman he's going to be frustrated when things go wrong.

"But with time to take a breath and reflect, he'll just keep working away at it.

"It's the nature of who he is that he never gives up. He'll keep his head down and keep working harder and harder."

Horner concedes if Red Bull are to hunt down runaway leaders Mercedes and Vettel is to win at all this season then Renault have to step up to the plate.

"We're very much in Renault's hands," added Horner.

"We are making progress, they're making progress, and Total on the fuel side have been making progress.

"But really, we are now where we should have been in January, and Mercedes obviously aren't standing still.

"But we've only had six races and there's still a long way to go in this championship."