Massa, Hulkenberg deals end the battle for F1's leading seats

Massa is due to visit Ferrari's factory on Tuesday for talks with team chiefs to thrash out a new contract for next year, which could be announced before the Indian Grand Prix.

And with options at the top teams having gone, Hulkenberg has already made his move, as the German is understood to have signed a deal with Sauber in the hours after the Korean Grand Prix.

At the front of the grid the seats are now all settled. Red Bull, McLaren and Mercedes have all officially confirmed their line-ups, while Lotus will retain Kimi Raikkonen and Romain Grosjean even though their contracts have not yet been signed.

The identity of Hulkenberg's team-mate is not yet known, with Sauber likely to wait until it has a clearer picture of its financial strength for 2013 later in the campaign.

The Swiss outfit is just 20 points behind Mercedes in the constructors' championship. If it can overhaul the German manufacturer it would earn several millions of pounds in commercial rights income, which could lessen the need for a pay driver in the second seat.

There will be pressure from Mexican sponsor Telmex to slot GP2 race winner Esteban Gutierrez in for 2013, but there are concerns that his inexperience could prove costly in such a competitive F1 field.

One option could be for Sauber to run Gutierrez in Friday practice sessions to help build his knowledge of F1. It could then give the second race seat to an experienced driver like Kamui Kobayashi, Jaime Alguersuari or Adrian Sutil.

Drivers chasing the second seat at Sauber are also pushing hard to secure a place at Force India, where Paul di Resta is set to remain for another year.

Force India is open-minded about its options, with a list of contenders that includes Alguersuari, Sebastien Buemi, Kobayashi and the team's Friday test driver Jules Bianchi.

Williams will retain Pastor Maldonado for 2013, while Valtteri Bottas' impressive performances for the team on Fridays this year - allied to the struggles that Bruno Senna has endured - makes it likely the Finn will be given a race chance.

Senna's best hopes of staying on the grid in 2013 could rest on a move to Caterham, where the future of both Heikki Kovalainen and Vitaly Petrov are unclear.

Kovalainen has been in talks with the team, while Petrov still has valuable backing from Russian sponsors despite suggestions there may not be enough to secure him a place in 2013.

Marussia will keep Timo Glock for next year, while Max Chilton is expected to line-up alongside him. Charles Pic, who has impressed in his rookie season, has been most strongly linked with a move to Caterham.

Pedro de la Rosa is staying at HRT, while his team-mate will be decided over the winter.