Who's are the likely candidates to replace Nico Rosberg? Mercedes starts discussions.

Mercedes bosses are set to gather for talks on Monday to begin what tech chief Paddy Lowe said will be a "very, very difficult" choice of sorting a replacement for Nico Rosberg.

Despite Rosberg having told team principal Toto Wolff privately via telephone of his retirement decision last Wednesday – just minutes after the pair had returned to Germany from a press event in Malaysia – the news was kept secret until Friday when the German announced it ahead of the FIA Gala in Vienna.

Having used the weekend as time to better gauge interest and better work out the team's options, the serious matter of actually picking the right candidate will now begin in earnest at Mercedes' Brackley headquarters.

The final decision will be discussed at length between Wolff, Lowe and non-executive chairman Niki Lauda, prior to approval by the Mercedes board.

But Lowe is in no doubts how tough a challenge the team faces to find someone who will deliver at the level that Rosberg did to help the team grab three consecutive constructors' championship trophies.

"We've a tremendous team that have secured all those records but we couldn't have done it without two fantastic drivers because they are there every race scoring the points," said Lowe on stage at the Autosport Awards on Sunday.

"[There is a] very low error rate and that is what it takes to get that statistic. So it is a big dent to lose Nico and they will be very, very difficult shoes to fill. So we will see where we get to it but it will be a big loss."

The likely candidates

While Wolff suggested over the weekend that every driver apart from Daniil Kvyat and Kimi Raikkonen had approached him for the seat, the realistic list of candidates is likely to be very small considering how late in the year it is.

Available experienced hands like Jenson Button and Felipe Massa are unlikely to be tempted back so soon after quitting, while obvious candidates like Sebastian Vettel, Fernando Alonso, Daniel Ricciardo, Nico Hulkenberg and Carlos Sainz are all contractually locked down.

Instead, it is looking increasingly likely that Mercedes junior Pascal Wehrlein will be the one that will be discussed first – to evaluate whether or not team bosses feel he is ready to make the step up to the works team for 2017.

Wehrlein scored a point for Manor this season, but it is understood he was overlooked by Force India as a replacement for Nico Hulkenberg because the Silverstone-based team's engineers much preferred the attitude of French youngster Esteban Ocon.

From Mercedes' perspective, Wehrlein is a known quantity, is already well integrated inside Mercedes, knows the simulator and team well, has tested extensively on Pirelli's 2017 rubber – and ultimately to pick any other driver would put question marks over why the Mercedes junior programme exists in the first place.

However, working against him is the fact that he has only raced in F1 for a year so the pressure of going up against Lewis Hamilton in a race-winning car would be immense.

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F1 witnessed last year how youngsters by the pressure of competing at the top too soon, with Daniil Kvyat's failure when he moved up to Red Bull after one season at Toro Rosso.

Should Wehrlein not tick the right boxes and a more experienced man is required, then the logical step would be - although more complicated and more expensive for Mercedes – to try to do a deal with Williams to release Valtteri Bottas for next year.

The Finn, whose career has been helped by Wolff, would deliver the consistency and the speed needed to guarantee a good constructors' championship position.

Mercedes could offer cash, or a reduction in engine price, plus even Wehrlein as a replacement in a bid to sweeten a deal – but Williams may feel that losing Bottas when it has a rookie Lance Stroll in its second car may be too costly.

What is clear, though, is Mercedes finds itself in an incredibly strange situation – of having potentially the best car on the grid but a huge headache in trying to find a driver it can put in it.

Gallery: Analysis of Mercedes' options for Rosberg replacement

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