NORTH Melbourne coach Dean Laidley could only scratch his head and wonder why in the wake of his side’s 18-point win over Collingwood.

Why is his side was capable of beating the Magpies, Hawthorn and the Bulldogs, and yet drop winnable games to St Kilda, Fremantle, Brisbane and Essendon. 

Nevertheless, Laidley was taking the win, and could not hide his pleasure at the persistence and resolve of his team.

"It was a terrific performance, I was really pleased for the boys - they were pretty hard at it all night and the pressure was enormous from everyone," he said after the Roos second win over Collingwood this season.

"Their attack on the footy was second to none."

Despite North struggling to convert possessions into goals in a wasteful first term, Laidley believed his side needed only to maintain its intensity and the wheel would turn.

"From basically half time, we went for it, we thought 'right, let's go for it here' - to their credit, that's what they did.

"We were able to put some scoreboard pressure on - and quickly - which perhaps we weren't able to do ... in the first half."

Laidley praised the work of his defence, particularly the effort of youngster Gavin Urquhart who was thrown the task on Magpie livewire Alan Didak.

But it was ruckman Drew Petrie that drew the most praise after his 11 marks, 26 hit-outs and two goal contribution.

 "It was super, he's pushed himself to another level - one of the true leaders of our footy club now and he's just willed his influence on the game," Laidley said.

"He's pretty-much done that all year -- he's been super."