The defending A-League premiers won't return to Australia until Friday morning when they land in Sydney and then travel to Gosford.
Arnold argued there was less in Saturday night's clash than what the scoreline suggested and said the Mariners would make the most of their home advantage in the second leg.
"I've had enough experience in the past and 2-0 scorelines are very dangerous and we're going back to Bluetongue and we're very positive that we can turn it around," he said.
"It was their night (on Saturday night) but they've got a huge schedule in front of them now with all the travel to South Korea and we go back to back to Bluetongue and we'll see how they pull up next Saturday when they arrive."
Roar talisman Thomas Broich, who was inspirational in a return to his best form, admitted the midweek ACL clash made for a tough assignment but a nine-match unbeaten streak (including seven wins) had ensured a spring in their step.
"It's good fun and the energy's there. It's when you struggle and you're losing games that you feel every step that you have to make, but for now the boys are feeling pretty good," Broich said.
While they didn't have it all their own way, especially when the Mariners threw down the gauntlet early in the second half, the Roar deserved their two-goal advantage from a pulsating encounter between the two fierce rivals.
Brisbane had 12 shots on target to four and squandered far more opportunities after Henrique scored in the eighth minute, such that coach Ange Postecoglou felt it would have been an "injustice" if they only claimed a 1-0 win.
It was Broich who delivered the pivotal play when he mesmerised three defenders in the 86th minute before laying off for Erik Paartalu to produce a blazing strike inside the left-hand upright.
"That helps us big time," Broich said.
The biggest concerns for the Roar surrounds Henrique who missed a seventh-minute penalty, his second straight failure from the spot, before ending the match with a hamstring problem.
-AAP
