Melbourne Victory suffered a 9-2 loss to City in the Foxtel Y-League Derby on Sunday night.
After Benjamin Carrigan opened the scoring for Victory at a wet Lakeside Stadium, Daniel Arzani, Joshua Cavallo and Denis Genreau struck for City.
Yazid Said scored early in the second half to give Victory hope, but another Arzani strike, a Braedyn Crowley hat-trick and late Ramy Najjarine brace saw City come out on top.
Victory head coach Gareth Naven said it was an unacceptable performance by his team.
"We as a group of players, staff and coaches need to understand that's not acceptable. It's as simple as that," he said.
He added: "There are things when we are in possession where we don't get the ball out quick enough, don't have early support.
"There are fundamentals, basic things to do, like win your tackles, demolish your opposition. There are all sorts of things you can do to achieve it. They achieved that a little bit more than we did, when you're supposed to do it.
"It's just those football, team smarts, which I think let us down big time.
"You've got to teach people how to be competitive and make sure the bloke you're up against, you want to make sure he has a bad night. At times we show it, at times we don't show it enough.
"There are individuals in the group that will do it, but it's a team sport, you need the collective to do it."
Victory took the lead in the 18th minute through Carrigan, who headed in powerfully after a cross from the right.
But City struck three times in the space of nine minutes.
Arzani picked out the top corner from just outside the area, Cavallo's free-kick from the right snuck in at the near post and Genreau headed in a third.
Victory pulled a goal back shortly after the break as Said tapped in after combining with striker Kenny Athiu.
City restored its two-goal lead 10 minutes into the second half thanks to another Arzani effort before Crowley curled in a free-kick.
Crowley scored twice more in the space of three minutes, including with another free-kick, before Najjarine netted a late brace.
Foxtel Y-League 2017/18 Round 3
City 9 (Daniel Arzani 25'/55', Joshua Cavallo 30', Denis Genreau 33', Braedyn Crowley 71'/74'/76', Ramy Najjarine 90+1'/90+2')
Melbourne Victory 2 (Benjamin Carrigan 18', Yazid Said 47')