A horror defensive lapse has stalled Melbourne City's A-League push as Macarthur came from behind to secure a 1-1 draw at Campbelltown Stadium.

The ladder leaders - fresh off a 7-0 win that ultimately cost Melbourne Victory coach Grant Brebner his job - found goals much harder to come by in Sydney's west and then paid dearly for some sloppy marking.

Up 1-0 and seemingly with the game under control, a Scott Jamieson throw-in near the Bulls' goal precipitated a series of events in the 77th minute the visitors will quickly want to forget.

Jamieson's one-two with substitute Marco Tilio didn't work out so well, Denis Genreau stealing the ball and scooting down the sideline.

It should have ended when Tilio did well to recover the ball but Kerrin Stokes made a meal of a relatively straightforward pass before Bulls sub Michael Ruhs picked up the crumbs and beat 'keeper Tom Glover to level the match.

City coach Patrick Kisnorbo didn't mince words about the blunder, despite 18-year-old Stokes' inexperience in the top-flight.

"I think we use age maybe as an excuse - I think it is called concentration. And it's a basic error," Kisnorbo told Fox Sports.

"He'll learn but unfortunately, he was the one that made that crucial error."

The Bulls got a head of steam from there and dominated much of the remaining play as they looked to snatch a win.

The best of those came in the 82nd minute when Matt Derbyshire tore down the right flank, Ruhs perhaps just a yard or two shy of the fired cross to get a foot on it.

Still, it was a night to remember for the solidly built teenaged midfielder.

"It was a big achievement for me to score my first A-League goal," he said.

But with 27 goals in their previous eight games, the City sharpshooters weren't quite done, Connor Metcalfe hit the crossbar with their best remaining chance of the contest.

Earlier City had gone ahead with some of the finishing that has marked them as the standout attacking team of the competition.

Jamieson delivered a pinpoint long bomb to Jamie Maclaren on the left wing and he backheeled for Craig Noone who delivered a sharp cross for Metcalfe to drive home a low left-foot volley on 59 minutes.

It had all followed a largely defence-orientated first half with few chances for either side.

The best fell to Maclaren, who with 19 goals already looks like the competition's Golden Boot winner.

The Socceroo wound up with only 'keeper Adam Federici to beat in the 19th minute but shot disappointingly wide.