The loss ended a four-match winning streak for the Jets but Culina believes the overall form of his side is good enough to overcome the Melbourne Victory on Sunday.
"I don't think it has affected us, other than the fact that we lost and we don't like losing," he said.
"We had a great run - we won four in a row and no-one else has done that this year, but we can't expect to win every game.
"It was disappointing in the fact that we lost 4-0 but we are like that sometimes; when we have an off day we really have an off day and that was the case in Perth.
"But psychologically it is behind us. Don't forget that even before the four in a row we won two previous games out of four, so that means we have won six out of the last eight - that is not a bad record. So we are still positive."