In one of the most interesting post-season windows in recent Formula 1 history, Felipe Massa has reversed his retirement decision made earlier this year and return to racing with his last team Williams; paving the way for Valtteri Bottas to join Mercedes, in the wake of reigning world champion's Nico Rosberg's shock retirement.

Although, if Bottas isn't selected as Rosberg's successor alongside Lewis Hamilton, Massa will not return, despite signing an initial contract worth €6 million for the whole year with the Grove team.

Bottas, 27, has been with Williams since he made his debut in the sport in 2013, but has failed to claim his maiden win thus far, despite earning nine podiums. And whilst he was formerly confirmed at Williams alongside young Canadian prospect Lance Stroll for 2017, Rosberg's departure, announced at the FIA's Press Conference in Vienna on 2 December, has opened up the top seat the Finn has been searching for.

With contract negotiations ongoing between Mercedes and Bottas, the deal is expected to be announced early in the New Year, with Massa's comeback likely to be confirmed on the same day.

Driver changes

Speculation had been rife as to who would replace Rosberg at Mercedes. Junior driver Pascal Wehrlein had been the favourite for a promotion from Manor, due to fellow Mercedes colleague and former Manor teammate Esteban Ocon stepping into the Nico Hulkenberg shaped hole at Force India.

This turn of events means that the 2017 grid is starting to have a more solid look to it, with just Sauber and Manor left to announce their partnership.

Allegedly, GP2 rookie sensation Antonio Giovinazzi is favourite for a Sauber seat after joining Ferrari as a reserve driver earlier this month. As for Manor, Wherlein is expected to stay on for 2017, but the backside that will be placed in the second seat is as of yet, unknown.