Britain's Jenson Button escaped serious injury in a high-speed crash during Saturday's free practice for the Monaco Grand Prix.
The 23-year-old missed the final qualifying session after being taken to hospital following the 180mph accident at the exit of the tunnel and is doubtful for Sunday's race.
Button's car pinballed between the barriers and although he wanted to take part in qualifying his BAR-Honda team decided not to take the risk.
Team boss David Richards said he would have a medical around lunchtime on Sunday and rated his chances of participating at "70%".
Richards also played down the significance of Button's detention in hospital, saying the driver was physically unharmed but had suffered slight nausea.
"They did a full scan and everything and the professor there just said he would prefer him to stay in overnight rather than to go sleep on a boat down in the harbour," he said.
"It was a fairly monumental accident. He was very coherent when I was chatting to him, he would have got back into the car this afternoon given half a chance.
"Twenty three-year-olds tend to put these things behind them," he added. "It would have been nice to get him back in the car a bit quicker but unfortunately that's not going to happen until tomorrow."
If he does race, Button will have to start from the back of the grid or the pit lane.
BAR technical director Geoff Willis said there were no signs that a car failure had caused the accident and that it appeared Button had triggered the crash by hitting the barrier.
Button appeared to clip the barrier as he exited the tunnel in the morning's second session.
His car hit the metal barriers which line the circuit on the right hand side, rebounded onto the guard rail on the left and then spun sideways before skidding down the escape road behind the harbour-front chicane into a third barrier.
Button, third in first qualifying on Thursday, remained in the shattered car as doctors attended to him for several minutes before being taken away in an ambulance.
Doctors said he had remained fully conscious with no visible injuries but had been winded by the heavy side impact.