Sergio Perez believes his clash with Pastor Maldonado in free practice at Monaco this morning was the cause of his qualifying crash.
The Sauber driver and the Williams made contact in FP3 before Perez crashed at the Swimming Pool right-hander in the opening minutes of qualifying.
The team checked the car after the practice accident and believed it was fixed, but Perez now thinks it could have caused the later smash.
"We cannot prove with the data that there was a problem, but looking at the onboard with the whole team, we all agree that there was a problem, and we think it came from this morning," said Perez, who also crashed out in Monaco qualifying last season.
"We changed most of the parts, but not all. We don't have enough sensors in the suspension to see what the problem is.
"The car was not 100 per cent. I arrived in the tunnel and I had massive understeer. In Turn 13 it was OK, then into 14 suddenly the car went straight. If you have a small problem like that here the first thing you find is the wall."
Perez believes the stewards were right to give Maldonado a 10-place grid penalty as a result of the FP3 incident.
"I don't know what Pastor was doing this morning," he said. "It was completely unnecessary.
"We were on a slow lap. I wanted to do a slower lap, but he wanted to go quicker so I went on the inside to let him by and he drove into me.
"It was a big shame because we had a really competitive car and I think we could have fought for a really good position. We had a great opportunity."