Who's in the race to partner Lewis Hamilton at Mercedes now Rosberg has retired?

Formula Spy's Thomas Maher looks to the future after Friday's shock announcement

Mercedes, Lewis Hamilton, Nico Rosberg,

Mercedes' Lewis Hamilton celebrates qualifying in pole position at Yas Marina Circuit, Abu Dhabi. Picture by David Davies PA Wire/PA Images

Out of the blue, F1's off season became sensational on Friday afternoon.

The annual FIA Prize Giving Ceremony is usually a by-the-numbers affair, with drivers praising their teams and sponsors and generally not causing too much of a fuss. That was, until Nico Rosberg took the opportunity on stage in Vienna to announce his retirement from Formula 1, just five days after wrapping up his maiden title by defeating teammate Lewis Hamilton by just five points after twenty one arduous races.

It's a shock decision, and a very brave one. Retiring from the sport at just 31 years old, Rosberg spoke of the reasoning behind his decision and cited finding it difficult to cope with the immense pressure of a title bid for the third year running: "This season, I tell you, it was so damn tough. I pushed like crazy in every area after the disappointments of the last two years; they fuelled my motivation to levels I had never experienced before.

"When I won the race in Suzuka, from the moment when the destiny of the title was in my own hands, the big pressure started and I began to think about ending my racing career if I became World Champion. On Sunday morning in Abu Dhabi, I knew that it could be my last race and that feeling cleared my head before the start. I wanted to enjoy every part of the experience, knowing it might be the last time… and then the lights went out and I had the most intense 55 laps of my life. I took my decision on Monday evening."

Not many are able to retire on their own terms and still at the top. One only has to look at Jenson Button's ignonimous exit in Abu Dhabi after 16 years racing to see how quietly a driver's career can peter out. Rubens Barrichello never even got a chance to say goodbye at the end of 2011 - he just didn't get a seat for the following season. Mika Hakkinen called time at the end of 2001 at 32 years old, having felt unable to handle the pressure of frontline racing anymore - he won his third last race and left because he wanted to.

Rosberg follows in the footsteps of Alain Prost, who quit after winning the title at the end of 1993. The Frenchman had the option of staying on at Williams for 1994, but this would mean partnering up again with Ayrton Senna - F1's most famously strained line-up. Rosberg's reasoning for departing is probably quite similar to Prost's, in that his relationship with Lewis Hamilton continues to be best described as "cool". 2017 was likely to see an instant resumption of that incredibly closely matched duel, and Rosberg simply doesn't want that stress any more.

As part of his departure statement, Nico paid tribute to the support he's had from home throughout his campaign.

The German champion is a very publicly family committed man, and he cited that the stress of 2016 "had an impact on the ones I love, too – it was a whole family effort of sacrifice, putting everything behind our target. I cannot find enough words to thank my wife Vivian; she has been incredible. She understood that this year was the big one, our opportunity to do it, and created the space for me to get full recovery between every race, looking after our daughter each night, taking over when things got tough and putting our championship first."

Rosberg also highlighted that he wants to be around to watch his daughter grow up and be there for all the important moments - a luxury not many can afford. With his money made, and a now successful title win behind him, he can afford to relax and bask in his achievements.

However, this has lit up the prospect of an even juicier driver line-up at Mercedes. Much has been made in recent days of Lewis Hamilton's purported 'threat' quit after the Spanish Grand Prix, and the question for Mercedes now is: Do they make Lewis the clear number one, and hire him a solid backup driver? That would be a very dull prospect, considering Mercedes aren't likely to drop from the front any time soon. It would keep their now only star driver happy, but Mercedes' Young Driver Program doesn't exist for no reason. Pascal Wehrlein has tested the W07 in 2016, including a tyre test in Abu Dhabi this week, but the German driver was passed over for promotion from Mercedes customer Manor to Force India just weeks ago. Presuming Mercedes AMG weren't aware that Rosberg was about to retire, then this doesn't express much confidence in Wehrlein. The man who got that Force India seat, Esteban Ocon, is only in the sport a wet weekend and, while he's fared well, untangling him from a recently signed deal and promoting him into the best car on the grid isn't particularly likely. So where do Mercedes look?

The obvious prospects are mouth-watering. Fernando Alonso would very much like that seat, and himself and McLaren are likely carefully poring through their contracts for next year. Like-wise, Sebastian Vettel is renowned for negotiating minimum points scores into his contracts - if he didn't score enough in an average 2016, might he be able to wriggle free of Ferrari and jump ship? The Red Bull drivers will be evaluated, but Daniel Ricciardo's and Max Verstappen's contracts are likely watertight, disappointingly. Watching Verstappen in a Mercedes treat Hamilton with the blase indifference he is famous for would make 2017 fun, even if Mercedes were two seconds a lap faster than anyone. Even Jenson Button, who celebrated retiring five days ago, might be convinced to return!

Regardless of Merc's eventual decision, Rosberg's retirement has sent shockwaves through the sport. Not since 1994 has F1 entered a season without the reigning champion. Not since Michael Schumacher's departure at the end of 2006 has such a coveted seat become available. It takes supreme confidence to walk away from the prospect of further future successes, and that's exactly what Rosberg has done. A worthy champion, and a man that can walk away from F1 having reached the very top.