Police believe a Sydney man left fighting for life on the side of a road with head injuries was assaulted in an early morning attack.

A man is fighting for life after being found on the side of a road suffering head injuries in Sydney's west.

Police believe a Sydney man left fighting for life on the side of a road with head injuries was assaulted in an early morning attack.

Police have named a man they are searching for after a 74-year-old was attacked in Sydney.