A security guard who happened to drive past shortly after the incident stopped and provided assistance.
The 56-year-old man was taken to Middlemore Hospital and has now been transferred to Auckland City Hospital in a serious but stable condition.
The other man was not hospitalised.
Detectives have this morning (Sun) cordoned off an area near St George St and launched an investigation.
Police are yet unsure of what led to the attack.
They are appealing to the public for sightings of the vehicle and have asked for anyone with information on the incident to come forward.