Puzzling case of injured man found by ute

A man found lying near a dinged-up ute in southwest Sydney suffered serious injuries - but not the kind investigators would expect him to have sustained in a crash.

The man is in Liverpool Hospital in a critical condition after he was found lying on the side of Stennent Road in Ingleburn about 2.10am on Sunday, near a ute that had mounted the gutter.

Detectives have not been able to speak with him yet and do not know what caused his wounds.

"They believe that they're not consistent with being involved in a crash," an NSW Police spokesman told AAP.

"There also wasn't a lot of damage to the vehicle," he said.

Investigators are trying to work out if the man was a passenger in the ute, and if so, what became of the driver.