Mr Buckley said that, while there weren't many pedestrians on the street at the time of the attack, there was a lot of vehicular traffic on the roads, especially on Heretaunga St.
"We are very keen to hear from anyone who may have seen the man being attacked, or who may have seen anyone acting suspiciously in the Heretaunga St/Allerton St area between 6.30pm-7pm. We're particularly keen to speak to a group of people who were standing outside a bar across the road from where the attack occurred.
"They may have seen the attack in progress or seen the attacker/s fleeing the scene."
Mr Buckley said the attack and robbery was violent and of some concern.
"It's important that we find the people responsible for this. The victim now has a serious injury that will require ongoing medical care and on top of that, he was robbed of a sizeable amount of cash and his cellphone."
Anyone with information about the robbery should contact Mr Buckley on (06) 831 0700 or information can be left anonymously on the Crimestoppers line: 0800 555 111.