“We will start looking at that on Monday,” Mercedes boss Toto Wolff said - but why was Mercedes so unprepared for Rosberg's decision? As recently as July Rosberg signed a new contract to stay with the Silver Arrows until the end of 2018.
“I'm super-happy to extend for another two years with my dream team,” Rosberg said at the time.
However he never told the heads of the team that his decision to retire if he won the championship was strengthening.
“He caught us off-guard,” team supervising boss Niki Lauda told German automobile magazine “Auto, Motor und Sport”.
How difficult will the hunt for a successor be?
If a cockpit at the team that dominated the competition for the past three years became available, you’d naturally expect a string of applicants. However, at the beginning of December many drivers are already locked into contracts for next season, especially top the top names.
In addition, 2017 brings a rule change that would make it more difficult to for Mercedes to take their own, relatively inexperienced, development driver Pascal Wehrlein who was with Manor in 2016.
Mercedes boss Toto Wolff said: “We will take the appropriate amount of time and check all variations to lock in the right way for the future.”
Who are the possible candidates for Rosberg's cockpit?
Wehrlein would be the simplest solution. After a solid debut season at Manor, the future of the Mercedes youngster is still unclear. It has also been speculated that stalwart Fernando Alonso would not turn down an offer from Mercedes after two frustrating years at McLaren.
However, it is unlikely that McLaren would be prepared to release the double former champion. Mercedes would need to negotiate hard with Ferrari, Red Bull or Williams if they wanted to get Sebastian Vettel, Max Verstappen or Valtteri Bottas.
Further options might be veterans Jenson Button or Felipe Massa who recently retired, but could be lured back with the prospect of wins. There was no Plan B for the this kind of situation, Wolff said.
What part would Mercedes superstar Lewis Hamilton play in the decision?
Hamilton has said he will not influence the decision about who his new team-mate will be.
“I just always asked to have equal rights,” he said. “As long we're treated fairly, it doesn't really matter who is alongside you.”
The 31-year-old did not want to name a preference.
“I've never needed a team-mate to be able to push me. The better the driver, the better it is for me when I finish ahead of them,” the three-times world champion said.
Hamilton's relationship with his previous partner Rosberg had deteriorated recently, and the team would be looking to avoid a similar situation in the future. That could make them less likely to choose Alonso as the pair had a bitter rivalry when they were together at McLaren which ultimately cost both of them the championship.
Rosberg rules out F1 comeback
Meanwhile, Rosberg has insisted he will “quite definitely not” change his mind and return to the sport after announcing his shock retirement from driving.
“When I was six years old and started out, the dream was very clear: I wanted to become Formula One world champion and that's what I pursued all along and it's mission accomplished for me, I've done it,” Rosberg said late on Friday as he collected his championship trophy in Vienna.
“It's a dream come true and now it's on to other things, with family first.”
Rosberg secured his first - and now only - title at the season-ending Abu Dhabi Grand Prix last Sunday by finishing second behind Mercedes team-mate Lewis Hamilton. He took the championship from Hamilton by five points.
“I never give up, so if I'd finished second I would have gone for another year, for sure,” Rosberg said.
Rosberg's contract with Mercedes was due to run to 2018 and the team must now quickly find a replacement to partner Hamilton for the 2017 campaign which will begin late in March in Australia.
Original source: Mercedes looks for Plan B after Rosberg quits