McLaren driver Lewis Hamilton was "gobsmacked" after what he described as a "shocking" Japanese Grand Prix.
While team-mate Jenson Button produced a brilliant drive to victory at Suzuka, Hamilton finished a distant fifth.
The Brit, 26, suffered a slow puncture, lack of grip and a clash with Felipe Massa for the second successive race.
"I had a bit of a shocking race to be honest," Hamilton told BBC Sport. "I didn't have any grip. I'm gobsmacked to be honest but that's the way it goes."
Hamilton made a strong start to run second in the early stages behind pole-sitter and early leader Sebastian Vettel, who was crowned champion after finishing third behind Button and Ferrari's Fernando Alonso.
And he was still in touch with the leaders despite a puncture that forced him into an early pit stop on lap eight.
But he fell away from the leaders through the rest of the race and eventually finished behind Red Bull's Mark Webber as well.
Asked by BBC Sport why he thought he struggled for pace, Hamilton said: "I think it's me and how I dial the car in.
"I don't know if I've dialled the car in as good as he [Button] has maybe. Who knows? I'm clearly not driving as well as he is.
"I'm not even thinking about next year. Today was one of the slowest races I've probably ever had in terms of performance so I just need to find out where I lost all that time.
"In qualifying, I was very close, but in the race I couldn't hold onto him to save my life.
"I just need to keep my head up and keep working hard. Hopefully in the next race we'll have another chance."
Hamilton arrived in Japan determined to put his collision with Ferrari driver Massa in Singapore behind him, but the pair, who lined up alongside each other on the second row of the grid, came to blows once again.
As they exited the 190mph 130R corner before the final chicane on lap 22, the two drivers came together, with Massa losing a front wing endplate.
McLaren team principal Martin Whitmarsh told BBC Sport: "I think he was a little bit distracted when he had the coming together with Massa because he was just about to come in here [the pits] and get a new set of tyres."
Hamilton added: "I can't see anything out of my mirrors and they vibrate so much down the main straight. I had no idea he [Massa] was there."
The 2008 world champion escaped punishment for the incident and later made a clean pass on Massa, but he lacked the ultimate pace to deliver on his early promise and finished fifth, 24 seconds adrift of the winner.