McLaren's hopes of securing the Formula One constructors' title this weekend were dented when Kimi Raikkonen suffered an engine failure in Friday's opening practice for the Japanese Grand Prix.
The Mercedes-powered team are two points clear of Renault with just the season-ending Chinese Grand Prix remaining after Suzuka.
McLaren can win the title on Sunday if they finish one-two, as they did at the last race in Brazil, and if Renault fails to score more than a point. Otherwise the title will be decided in Shanghai on Oct 16.
The engine failure will cost Raikkonen 10 places on the starting grid, leaving the Finn with a tough task despite the evident superiority of his car in recent races.
Raikkonen, winner six times this year but beaten to the drivers' title by Renault's 24-year-old Spaniard Fernando Alonso, pulled off the track halfway through the session with smoke and flames spewing from the engine.
The Finn has been plagued by misfortune this season, with blown engines in practice wrecking his hopes of pole position in France, Britain and Italy.
McLaren's Spanish test driver Pedro de la Rosa posted the fastest time in the one-hour session, lapping the Honda-owned circuit in one minute 30.532 seconds, 0.543 seconds faster than Toyota's Brazilian reserve Ricardo Zonta.
Briton Jenson Button, in a Honda-powered BAR, was the quickest race driver with the third best lap, more than a second and a half slower than De la Rosa.
Briton David Coulthard was fourth in a Red Bull, ahead of McLaren's Colombian Juan Pablo Montoya.
Alonso, who became Formula One's youngest champion at the last race in Brazil, and Italian team mate Giancarlo Fisichella, lapped sixth and seventh fastest respectively.
Ferrari, who have won the last five races at Suzuka, continued to look out of sorts with seven times world champion Michael Schumacher languishing in 18th place on the timesheets and Brazilian Rubens Barrichello 16th.
Japan's Sakon Yamamoto made his debut at a grand prix weekend as third driver for the Toyota-powered Jordan team.
He will not race on Sunday but performed creditably enough, setting the 20th time and lapping faster than Indian team mate Narain Karthikeyan and Portugal's Tiago Monteiro.
