Fernando Alonso admitted it would be an uphill task for him to claim his third consecutive world championship drivers' title after the Spaniard crashed out of the Japanese Grand Prix.

Alonso lost control of his McLaren at Turn Five of a sodden Fuji Speedway and ploughed into the safety barrier while running in fifth place to end his afternoon after 42 of the 67 laps.

The Spaniard was then forced to look on as championship leader Lewis Hamilton drove home the advantage with a fourth victory of the season to open up a 12-point gap at the top with just two races to go.

Alonso conceded it was unlikely he would be able to overcome such a deficit.

''I'm not throwing in the towel but unless Hamilton retires, we have to be realistic and see that it's very difficult to recover six points per race.

''It means winning the two races and him finishing fifth or sixth. He hasn't had retirements this year but maybe it will come in the last two races.

''So maybe I can race a bit more relaxed now. But I'll keep fighting because, as last year showed, anything can happen.''

Alonso had been hit by Sebastian Vettel's Toro Rosso seven laps prior to his accident and team boss Ron Dennis confirmed the incident had contributed to the Spaniard's downfall.

''Once his car had been damaged, it was very difficult for him to drive and keep the pace but he did a good job,'' said Dennis.

''And it just got away from him when the water got a little heavier, so it's just one of those things.''

The treacherous conditions were the subject of much debate among the drivers once the race had finished. But while conceding they played their part, Alonso refused to blame the decision to start the race after 19 laps behind the safety car for harming his championship chances.

''I was happy to start the race,'' he added. ''It was very difficult to see anything because of the intensity of the spray, especially down the straight.

''So I didn't see Vettel in my mirrors and was surprised when he hit me. I think the car was damaged quite a bit but I could carry on.

''But when I was braking for Turn Five, I just aquaplaned and spun. Unfortunately, the barriers at that corner are very close to the track and that was it.''

Alonso pitted from second on lap 27 only to rejoin in eighth.

Hamilton, on the other hand, came in a lap later and managed to come out in third place and establish a healthy advantage over his rival with a less congested track ahead of him.

But Dennis insisted the Spaniard was merely a victim of bad fortune as opposed to any mistake over his strategy.

''There was nothing wrong with the stop, it was just very long because we put fuel for the end of the race and he came out between three or four slow cars which hampered his progress through the field,'' said Dennis.