Lewis Hamilton is the 11/10 favourite for victory on Sunday despite heading to the Japanese Grand Prix 23 points adrift of Nico Rosberg in the title race.
The 31-year-old was on course to move clear of Rosberg in the championship race before he was forced to retire in Malaysia last weekend with only 15 laps remaining.
The broken engine arrived back in Brixworth on Tuesday - where it will undergo analysis - but Mercedes remain none the wiser as to why the Briton has been scuppered in at least three grands prix, while Rosberg has enjoyed a relatively trouble-free year.
Hamilton is 5/1 not to complete the race on Sunday and Mercedes technical boss Paddy Lowe said on Thursday: “We are continuing to investigate the issue with his engine and are doing everything we can to ensure that it is first understood and then contained for the remainder of the season.”
It should not be forgotten though that he has the best reliability record of any world champion in the sport's history. His failure to finish on Sunday was only his 11th from 183 starts (six per cent).
How Hamilton responds in Japan will be imperative to his chances of making history this year by becoming the first British driver to win four titles.
He has won in Japan on three occasions – at Nagoya in 2014 and again last year, while also turning in a masterful display at Fuji in the wet to triumph back in 2007.
Rosberg is 13/10 for a victory which would see him take another big step towards the title, while Daniel Ricciardo is 7/1 for a second successive win after his triumph in Malaysia.
Circuit length: 5.807 kilometres/3.608 miles
Race distance: 307.471km/191.053 miles
2015 pole position: Nico Rosberg (Mercedes) 1min 32.584 secs
2015 winner: Lewis Hamilton (Mercedes)
2015 fastest lap: Lewis Hamilton 1min 36.145 secs
Number of corners: 18 (eight left/10 right)
Tyre compounds to be used: soft/medium/hard
Overtaking chance: low
Engine severity: high
Brake wear severity: very low
Number of safety cars deployed since 2009: Seven