Highlights - Japanese GP first practice
Heavy rain played havoc with Friday practice for the Japanese Grand Prix at Suzuka as championship leader Jenson Button sat out the final session.
Button and Rubens Barrichello, his Brawn team-mate and title rival, stayed in the garage as second practice was reduced to just 13 minutes of action.
Force India's Adrian Sutil clocked the quickest time of the second session.
McLaren's Heikki Kovalainen set the fastest time of the day with his time of one minute 40.356 in first practice.
Sutil's effort of one minute 47.261 was enough to top the timesheets in a second session that offered very little indication of real race pace.
Hamilton targeting podium finish
Red Bull's Sebastian Vettel, who needs to finish on the podium in Japan to keep his slender drivers' championship chances alive, was second quickest.
Force India's Vitantonio Liuzzi was third fastest as the lap times tumbled when more drivers took to the track as some of the surface water cleared.
Brawn abandoned the second session completely, along with Kovalainen, as they opted to preserve their wet weather tyres for the weekend ahead rather than involve themselves in the frantic finale to the second session.
F1 WORLD CHAMPIONSHIP MATHS
Button will win the title in Japan if...
He wins and Barrichello is lower than third
He is second and Barrichello is lower than fifth
He is third and Barrichello is lower than seventh
He is fourth and Barrichello is lower than eighth
"The wet track meant that we opted for a reduced programme today," confirmed Brawn team boss Ross Brawn.
"As the weather forecast shows a dry qualifying and race and with limited wet weather tyres, we felt that there was nothing further to be learnt from running again this afternoon."
Button added: "I feel sorry for the fans at Suzuka today but unfortunately we can't get any useful information in these conditions with so much water on the track."
The Englishman will win the championship if he scores five more points than Barrichello in Japan.
Barrichello vows to go flat out for victory
After over an hour of inactivity Toro Rosso's Jaime Alguersuari took to the track with 25 minutes of the session remaining but after tip-toeing around in one minute 56.848 he returned to the garage.
"There is a big river from Turn Seven to Turn Eight and it is quite dangerous," reported the 19-year-old Spaniard on team radio.
Just over 10 minutes later Fernando Alonso emerged from the Renault garage to slice over eight seconds off the fastest lap and encourage others back out onto the track.
McLaren's Lewis Hamilton was fourth fastest in the afternoon and the defending world champion savoured the challenge of his first race at the famous figure-of-eight-shaped circuit.
"This is the best track I've ever driven," Hamilton said afterwards. "It's something very special for me and I had a great time today, even though it was wet.
"We didn't do much running - we weren't supposed to be running this afternoon, but I couldn't help it: I just had to go out and have a little bit of fun!
"I've heard it's going to be dry for the race, I'm just looking forward to getting out there in the dry and seeing how fast you can push around here."
The medium downforce Suzuka track with its mix of high and low-speed corners is expected to suit the Red Bulls but Force India and a revitalised McLaren will also be hoping to continue their good recent form.
Button wary of Red Bull threat
Teams usually use Friday's two 90-minute run-outs to experiment with fuel loads and assess any changes and developments they have made to their cars, but it will be difficult to gauge much from Friday's rain-affected sessions.
There was a new face in one of the Toyotas as Japanese test driver Kamui Kobayashi stepped into the cockpit to replace the unwell Timo Glock, and the 23-year-old put in a solid display as he finished 19th and 12th in front of his home fans.
Glock, who is suffering from a heavy cold and fever, reportedly has a temperature of over 39C but he is expected to be fit for Saturday's final practice and qualifying sessions.
Highlights - Japanese GP second practice