Former Formula 1 racer Sir Stirling Moss believes that Lewis Hamilton will find this weekend's Brazilian Grand Prix the most "difficult".
The 27-year-old will bid farewell to McLaren in South America for the final race of the season as he prepares to embark on a new career at Mercedes.
"I think he will find it difficult because there is no doubt McLaren have lost a quality driver, and from his point of view, people are wondering why he did it," Moss told BBC Radio Five Live.
Meanwhile, the race for the Championship goes down to the wire with Red Bull's Sebastian Vettel and Ferrari's Fernando Alonso both in contention for the title.