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Janko latched back on to the ball to attempt a follow-up shot, but his effort flew over the bar.
Sydney created a number of chances in the first half, one of which involved Janko yet again after the ball was cut back to him in the penalty area, but two Brisbane defenders closed him down to snuff out the danger.
In the 27th minute, Sydney broke the deadlock through Janko, who received the ball halfway between the centre circle and the penalty area and after controlling the ball with his chest, he unleashed a shot which bounced into the back of the net with the goalkeeper off his line.
Brisbane searched for the equaliser, but struggled to create chances, with the biggest falling to Dimitri Petratos, who struck a first-time effort that was easily saved.
Sydney came close to doubling their lead in the opening seconds of the second half when Janko attempted a left-foot volley, but the ball sailed over the bar.
Brisbane had the majority of possession as the half went on, but little threat was created from the home side as another effort from Petratos missed the target.
Sydney looked as though they were beginning to tire as the match went on, which opened up opportunities for the hosts, one of which came from Petratos yet again, who launched a header towards goal from Shane Stefanutto's cross, but his effort went over the bar.
Brisbane's attempts to grab a late comeback eventually came to nothing as Sydney were able to hold on to their lead to take maximum points.