American Scott Speed said Alex Wurz's move during the British Grand Prix was too optimistic after the duo clashed in the race.
Williams driver Wurz dived down the inside of the Toro Rosso right after Speed had let race leader Fernando Alonso lap him.
Speed didn't see Wurz was there and made contact with the Williams, his car being too damaged to continue.
"It all came to a quick end as we were letting the leaders by," said Speed. "It was certainly a bit of a complicated incident, because I knew that for about half a lap the leaders were quite close behind us, but Alex wasn't letting them by.
"When I did, I knew that me Alex and Trulli were so close I decided to let Fernando by at the same point as it would have been foolish to hold the race leader up for so long. As we went into the next corner, really tight together, Alex decided to take a very optimistic move down the inside but he couldn't hold it and ran wide into me.
"I didn't see Alex until we were in the corner. I went narrow to try and protect my position because I didn't want to brake late and run into the back of Fernando."
Speed's teammate Tonio Liuzzi completed a poor day for Toro Rosso, the Italian going out of the race with just four laps to go after suffering a gearbox problem.
It was Liuzzi's seventh retirement in nine races.
"Yet another retirement through a mechanical failure with the gearbox," said Liuzzi. "We need to work on reliability as this is our main problem at the moment.
"I had problems from about lap 15 onwards as something got stuck between my back and my seat, so it was really uncomfortable to drive, especially as this is a high speed circuit so it was very painful.
"That meant I was unable to push as hard as I wanted because of the pain. I also had a lot of understeer right from the start."