Perth Glory has retaken the whip hand in the chase for the national soccer league premiership and finals series bonus points with a 6-1 thumping of Wollongong on Sunday night.

And the Glory can thank the resurgent Northern Spirit for its two-point margin at the head of the NSL table after the Spirit knocked Olympic Sharks off the top with an upset 3-2 win.

Spirit substitute Adam Kwasnik struck twice in a thriller as his side fought back from 2-1 down, with his side now looking likely to gate-crash the top six and seal a playoff.

The Spirit has only lost once in its past six matches and is now four points behind sixth-placed South Melbourne with two games in hand.

Kwasnik was on the field six minutes when he scored to level the match at 1-1 after Ante Milicic had converted a penalty two minutes into the second half.

Olympic quickly charged back with a Franco Parisi goal, before Kwasnik struck again to make it 2-2.

With the final whistle only seconds away, Andy McDermott smashed a 25 metre free kick into the bottom corner of the net to finish a remarkable final 10 minutes and give the Spirit victory.

"I would have been ecstatic to come away with a draw and it is unbelievable to have a win," Spirit coach Lawrie McKinna said.

"Five or six weeks ago I said I would love to make the semi-finals and I now honestly think we can get there."

South Melbourne is looking decidedly vulnerable to the Spirit's late charge after a dismal 1-0 loss to the Melbourne Knights in the local derby at Knights Stadium.

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