Ferrari's world champion Kimi Raikkonen said he had no explanation for the run of four races without a point that has wrecked his title defence.

"It's difficult to find the right words," the Finn said. "Racing at night or during the day, this is definitely not my year.

"Obviously I'm really sad about this situation. I can't explain this dark period," continued Raikkonen, who crashed out of last weekend's inaugural night-time Singapore Grand Prix while in fifth place.

Raikkonen said he had lost a lot of time in final practice with a steering wheel problem, a delay that compromised his qualifying.

He said the tyre pressure was too low at the start of the race, which was then destroyed when he had to pit immediately behind Brazilian team-mate Felipe Massa after the safety car was deployed.

Raikkonen still managed to set the fastest lap of the race before riding high over a kerb and hitting a wall while chasing Toyota's Timo Glock.

"Once again we had the right speed at Singapore but not when it was really necessary," he said.

"The fastest race laps aren't worth anything, if you don't combine them with the situation when they really count."

Raikkonen is fourth and 27 points behind McLaren's championship leader Lewis Hamilton with a maximum of 30 still to be won from the three races remaining.

Tram effect

Red Bull have identified a tram as the likely culprit for Mark Webber's retirement in the Singapore GP.

The Australian, who has been dogged by bad luck in a 118-race career, was on course for a podium finish in the first night-time grand prix when his car's gearbox tried to select two gears at once and broke on lap 30.

Team boss Christian Horner said that it appeared a sudden electrical surge at turn 13 was responsible.

Webber was running behind Renault's eventual race winner Fernando Alonso and might have finished second after pitting before the safety car was deployed for the first time.