Fernando Alonso says Kimi Raikkonen spun on his own before the dramatic crash that put them both out the Austrian Grand Prix.
As Raikkonen lost control of the Ferrari, Alonso found himself with nowhere to go, and his car ended up on top of Raikkonen's after hitting the barriers.
Although the replays did not show how the Finn had lost his car, Alonso said he simply lost the rear because of the poor grip.
Raikkonen was one of only four drivers to start with the harder tyre compound.
"He was sliding a lot out of Turn 2," said Alonso. "I think there was a big difference between the soft and supersoft tyres.
"He started sliding, going left and right, left and right, and I was on the left and at one point he lost the car and I was there.
"It was a bit weird, because if someone hits you on a corner that can happen, but that the cars are sliding so much in fourth and fifth gear was a bit strange.
"This time it happened to him and I was in the wrong place."
He admitted he was concerned for Raikkonen when he realised there was a car below him.
"I saw I had a Ferrari below me in the mirrors, but I didn't know where he was," he said. "I thought I was alone.
"I tried to get out as quickly as possible to see if he was okay. I saw him removing the steering wheel so I was relieved," added Alonso, who had to visit the medical centre after what he said was a 34-g impact.
Test now "crucial"
McLaren introduced an upgrade package for this race, but Alonso and teammate Jenson Button's weekend was plagued by problems and they did hardly any running at all.
The Spaniard, who was the man in charge of running the new parts, admitted this week's post-race test will be vital for McLaren given the lack of running during the weekend.
"It was going to be a race in which we would have run at the back, but we couldn't do a single lap," Alonso added.
"Jenson also retired and I would have done the race by myself without any comparison, so anyway, a pretty bad weekend for us in terms of information.
"In terms of results we knew we would be compromising them with the engine changes, so the tests this week are almost crucial."