Police are investigating following an assault that occurred in Wallan last night.
Investigators have been told the victim had stopped at a service station on the Hume Freeway about 7.30pm.
Whilst he was at the bowser at the service station, a verbal altercation took place between the victim and a truck driver, who had also stopped his truck at the service station.
The truck driver struck the victim to the side of the head with a metal pole before getting back in his truck, believed to be a white semi towing a single trailer, before driving north onto the freeway.
The truck driver is perceived to be Caucasian in appearance, bald with a beer belly and was wearing shorts and a grey t-shirt at the time.
He is believed to be aged in his 40s.
The victim, a 24-year-old Fawkner man, sustained serious head injuries and was taken to hospital.
A crime scene has been established at the truck stop and investigators are urging anyone who witnessed the incident or with information leading to the identity of the truck driver, to contact Crime Stoppers on 1800 333 000 or submit a confidential crime report at www.crimestoppersvic.com.au