The 38-year-old has undergone surgery to have his nose reattached after he was attacked at his home in Leichhardt on Tuesday afternoon. The attack is believed to have been captured on CCTV camera.
Mr Zervas, whose brother Anthony was killed in a violent brawl between rival bikie gangs at Sydney Airport in 2009, was at his Norton Street unit about 5pm on Tuesday when an unknown man confronted him.
Inspector Naomi Moore, from the Leichhardt local area command, said the offender bit off part of the man's nose before fleeing down Norton Street.
"I would say that approximately half of his nose was bitten off," Inspector Moore said.
"He was able to salvage it and took it off to hospital, believe it or not."
Inspector Moore said it was not clear whether the men knew each other or why the attack occurred.
But Fairfax Media understands detectives are investigating Mr Zervas' bikie links as they continue to hunt for his attacker.
Inspector Moore said detectives hoped to retrieve CCTV footage of the assault and review it on Wednesday.
"We're in the very early stages of the investigation, and hopefully today we will be reviewing footage," she said.
"We know that the victim lived there in a unit on Norton Street, and the other person came to his premises.
"The detectives are hoping to speak further to [the victim] today at some stage."
It is not the first time Mr Zervas has been targeted.
In 2009, his brother and Hells Angels associate Anthony was killed in front of shocked travellers at Sydney Airport during a violent brawl between rival bikie gangs. Anthony was bludgeoned with a bollard during the brawl and stabbed in the chest and abdomen.
The only man found guilty of Anthony's murder, former Comanchero bikie boss Mahmoud "Mick" Hawi, had his conviction set aside last month and will face a retrial. Hawi was granted bail this week following amendments to the Bail Act that came into effect a month ago.
A week after the airport brawl, Mr Zervas was shot multiple times while getting out of his car in front of his mother's house in Lakemba.
The previous year, a tattoo parlour Mr Zervas had opened in Brighton-le-Sands was firebombed, after it was targeted in a number of drive-by shootings.
Police set up a crime scene at the Leichhardt unit complex on Tuesday afternoon and forensic officers examined the area.
Detectives have appealed for anyone who saw anything suspicious in the area or on a nearby stretch of Parramatta Road at the time to contact Crime Stoppers on 1800 333 000 or visit the Crime Stoppers online reporting page.