McLaren's Jenson Button set the pace as his title rival Sebastian Vettel recovered from an early crash in practice for the Japanese Grand Prix.
To keep his title hopes alive, Button has to win in Suzuka on Sunday and hope Red Bull's leader fails to score.
The 2009 champion led both sessions, with Fernando Alonso's Ferrari second fastest overall ahead of Vettel.
McLaren's Lewis Hamilton caught traffic and was eighth, behind Mark Webber's Red Bull and Felipe Massa's Ferrari.
Vettel's crash at the second Degner corner provided some late excitement in an otherwise fairly sedate opening practice session at the challenging Suzuka circuit.
The defending champion added to the drama by running along the track, rather than waiting to be picked up by the marshals, leading to speculation that he was trying to stop the TV cameras filming the damaged front section of his car.
"It was a classic mistake around Degner One," said BBC 5 live analyst Anthony Davidson. "But it was a mistake nonetheless.
"He lost the front end, felt the rear was a bit light, let the car run out wide and then he was on the gravel and paid the price."
Vettel insisted on Thursday that he was not going to approach this race any differently than any other, and after first practice he told BBC F1 pit-lane reporter Lee McKenzie that the crash was the best reminder he could have had to focus on what he was doing on track rather than the championship.
"It was not really a big mistake," he said. "Maybe at that moment I was not 100% awake, and mistakes around here can be quite costly.
"I went off and tried to come back, tried to slow the car down as much as possible but didn't make it and hit the wall slightly."
Button finished runner-up to Vettel at the last race in Singapore and is the only driver who has a mathematical chance of stopping the German from defending his Formula 1 crown.
To do that, the 2009 champion has to win each of the remaining five races and hope Vettel does not win a point.
Button has commented here that mistakes are punished at Suzuka and realistically he will need Vettel to continue making errors this weekend.
It was a straightforward day for the McLaren driver, who is searching for his first win in Japan.
Button headed Hamilton in the morning and eclipsed Alonso by 0.174secs to top the timings again in the afternoon. But the Red Bulls appeared dominant when the teams were doing their race-simulation runs at the end of the second session.
"They are in a league of their own," Davidson said.
Button added: "The car feels good round here but we don't really know what to take from today in terms of where we stand.
"We need to improve a lot more to really feel confident we can challenge the Red Bulls.
"There are a few areas that are still a bit weak in terms of balance but hopefully we can find that overnight.
"I think the Red Bull is still the car to beat."
Alonso, meanwhile, believes Ferrari have made a step forward from Singapore.
"We hope to be able to fight with McLaren and Red Bull, but we know it won't be easy," said the Spaniard.
"What we can say is that the feeling from today is a little bit more encouraging than in previous races."
Hamilton was subdued when speaking to the media in Japan about his clash with Ferrari's Felipe Massa at the last race in Singapore.
The 2008 champion was also determined to put the latest controversy behind him but he got held up in traffic when he was out trying to set his fastest lap with the car in qualifying trim on softer tyres and finished 1.344secs off Button's pace.
Nevertheless, he is optimistic that he can have a strong weekend.
Hamilton, though, was more optimistic.
"Looking at the times, I think Red Bull typically carries less fuel than us during Friday's long-run practices - that's often been the case throughout the year - and we're often closer in the races," Hamilton said.
"I think our long-run pace, particularly on Jenson's car, looks good: I think we've got a good chance of being very competitive. Our pace over a single lap also looks very good."
Vettel lost only eight minutes in the second practice as the team worked through the lunch break to mend his damaged Red Bull.
When he emerged he also lost time under a backed up field of cars and set the third fastest time, 0.194secs behind Button.
Williams driver Rubens Barrichello, Renault's Bruno Senna and Japanese Sauber driver Kamui Kobayashi were caught out by fast and narrow Suzuka during second practice.
Barrichello also came unstuck at Degner One, taking his Williams backwards into the barriers and putting him out of the session.
"That's not a mistake you'd expect Rubens to make," said Davidson. "When you're desperately looking for a contract for next year it's a misjudgement."
Williams's problems mounted when team-mate Pastor Maldonado retired his car shortly afterwards.
Senna fared slightly better as he managed to keep his engine going and was pushed out of the gravel after going off at Turn One.
Kobayashi had a bumpy, sideways ride through the awesome 130R corner - where cars reach 190mph - and did brilliantly to keep his car on the circuit.
"Save of the century from Kobayashi," said BBC F1 commentator Martin Brundle on Twitter. "Stood on the bank at 130R watching as he opens DRS and spins 190mph corner and didn't hit a thing!"
After the session, Hamilton, Michael Schumacher, Sebastien Buemi, Heikki Kovalainen and Bruno Senna were called before the stewards for ignoring yellow warning flags.