Brisbane Roar coach Ange Postecoglou admits second-placed Central Coast Mariners are his side's biggest danger for this season's A-League title.

At yesterday's A-League finals launch, Posteocglou was quizzed on who he thinks poses the greatest threat to his team's pursuit of taking the Premiership/Championship double and his answer was not at all surprising.

The Roar take on the Mariners at Bluetongue Stadium on Saturday in the first leg of their two-legged semi-final and Postecoglou was remaining cautious of Graham Arnold's men.

"Central Coast finished second and by a clear margin, they have to be the ones (we fear most)," said Postecoglou.

"I think apart from ourselves they're probably the most consistent side in the league. They haven't missed a beat and they're hitting form heading into the finals. We're expecting a tight contest."

In response, Arnold was also treading carefully ahead of the clash.

"We've played against Brisbane three times. We know what they're about, they know what we're about. It comes down to performance on the night. The last game (3-3 draw at Bluetongue Stadium) gave us a lot of confidence," he said.