"He was taken to hospital for treatment and has now been discharged.
"Police investigating the assault are seeking information from the public as to what happened."
Murray said anyone who saw the assault or who can provide information about a person of interest was being sought.
The attacker is described as Māori or Pacific Islander, between 30 and 40 years old, of large build, with a beard and wearing a yellow high-vis jacket.
"Information can be passed to police via 105, quoting file number 220607/6363," Murray said.
"Alternatively, information can be passed anonymously to Crime Stoppers on 0800 555 111."