Nico Hulkenberg says it was too risky to accept a two-race deal at Lotus

German worried about comparison with Romain Grosjean.

Nico Hulkenberg has admitted the reason he turned down the chance to race for Lotus in the last two grands prix of the season was because of concerns about how being beaten by Romain Grosjean might damage his reputation.

The German visited Enstone to discuss the possibility of replacing Kimi Raikkonen in both Austin and Brazil after the Finn decided instead to undergo back surgery. Hulkenberg is also in the running for a full-time Lotus seat in 2014 but without the guarantee of a drive then, he opted to stay put at Sauber.

Felipe Massa confirms he is to leave Ferrari at the end of this season

Brazilian's place at the team set to be taken by Kimi Raikkonen

Felipe Massa has confirmed he is to leave Ferrari at the end of the season.

The Brazilian's place at the Scuderia is set to be taken by Kimi Raikkonen, although an official announcement outlining the team's 2014 line-up is not expected until Wednesday.

Massa, who only narrowly avoided being dropped by Ferrari 12 months ago before earning a one-year contract extension, has endured a troubled campaign, finishing on the podium just once and garnering half the points of team-mate Fernando Alonso.

In an longer message on his Instagram page, which was posted alongside a picture of his victory celebrations from his home Brazilian GP in 2006, Massa said: "From 2014 I will no longer be driving for Ferrari. I would like to thank the team for all the victories and incredible moments experienced together.