Robert Kubica said he assumed Mark Webber had not realized he was so close when they touched on the first lap of the Italian Grand Prix.
The incident forced Webber to retire - and effectively ended his world championship hopes - while Kubica sustained wing damage and had to pit for repairs. He later dropped out with an oil leak.
"I made a very good start and was in quite a good position before the first braking point," said Kubica. "I was on the left-hand side of Mark Webber. I guess he did not see me at all. Mark pushed me on the grass while I was on the brakes. Although I managed to come back on the track, we touched in corner one.
"In Roggia he was on the outside and slightly in front of me. When we were going into the first apex unfortunately again I was not able to avoid him.
"I ended up with a damaged front wing, but am not sure how this happened as it could have been with my fight with Mark or I could have hit a curb."
While Kubica's race quickly fell apart, his teammate Nick Heidfeld made rapid progress and came through from 15th on the grid to seventh - to his delight.
"I'm totally happy, as for me it was a great race," he said. "Coming seventh may not sound fantastic, but from 15th on the grid that really was the best I could do today.
"The start itself wasn't good at all, I almost lost positions. But then in the first corner I managed to overtake one car on the outside and then in the chicane I went to the inside to overtake Jarno Trulli.
"On lap three I overtook Giancarlo Fisichella, which I thought would be impossible because he has KERS on his car.
"Then when I was behind Sebastian Vettel I started to save fuel. After our pit stops he was behind me, and I was eighth before Lewis Hamilton crashed on the last lap and I benefited by scoring one more point."