McLaren's Lewis Hamilton thinks winning this year's world title could be beyond him after he lost more ground to his rivals at the Japanese Grand Prix.
Hamilton finished fifth and now lags 28 points behind championship leader Mark Webber, who was second as Sebastian Vettel led home a Red Bull one-two.
Ferrari's Fernando Alonso also came third as Hamilton's gearbox struggled.
"These guys continue to pick up points," he said. "It will be very difficult, but we'll keep pushing."
Just three races of the 2010 season remain and although Hamilton - who started the race 20 points behind Webber - managed to cross the finishing line for the first time in three grands prix, the Englishman had a difficult weekend overall.
He was penalised five places on the grid for changing his gearbox, leaving him to start eighth.
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The 25-year-old 2008 world champion then looked certain to finish ahead of his team-mate Jenson Button but, running with good pace in fourth position with 10 laps remaining, he lost third gear and his compatriot was able to pass him and finish a position higher.
"It's a bit disappointing for myself and my team," he told BBC Sport.
"We worked very hard, as always, and we're doing everything we can to score points.
"I made a mistake on Friday, then we had the gearbox problem. Then losing third gear I lost ground to Jenson.
"But I'm just thankful and happy I saw the end of the race, it's been a while.
"You have to try and remain optimistic, but I didn't think I'd make it [when I lost third gear]. It was making a lot of noise. But I had a big gap behind me so I could waste a bit of time.
"Still three races to go, still 75 points available. But these guys continue to pick up points. It will be very difficult, but we'll keep pushing."
McLaren team principal Martin Whitmarsh refused to give up the title fight for either Hamilton or the defending champion Button, who sits fourth in the standings.
But he admitted it will be tough for them.
"It hasn't run to plan," he told BBC Sport. "We've come away with some reasonable points. It's not a great day, but not as big a disaster as it looked at some points this weekend.
"It's tough [the championship]. Anything can happen. This was damage limitation, to an extent, but I think we showed here the pace isn't too bad.
"We've got to improve the car and carry on racing. We've got some more performance coming through, a new front wing we didn't race here. And a new rear wing."
Button - the only driver inside the top 10 on the grid to start the race on the harder tyre at Suzuka - admitted the defence of his world title will be difficult, and said he felt McLaren did not pit him early enough to get the best out of his alternate strategy.
Unless we're competitive in Korea, it's going to be very tough
McLaren's Jenson Button
"It's getting more and more difficult, and unless we're competitive in Korea, it's going to be very tough," he said.
"I'm still in the same position I was coming into this race. The Red Bulls were quick here - they were unbeatable - and Fernando [Alonso] was quick in the Ferrari.
"We have to hope that when we put a [new] package on the car in Korea, we get the best out of it.
"We came here with new parts - some of them worked well, and some of them need some work."
"I have to have a look at the data, but to stay out when they all pitted was probably the wrong thing. But whatever strategy we did today, fourth was probably the best we were going to finish."
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